Jeremih floats on his current radio hit, “Planes.” He darts around the spare beat with impeccable precision, he creatively combines Migos-style triplets with choppier patterns, all while hitting high notes in that sparkling, unique voice. And then the song’s guest rapper, the MC with the highest-selling rap album released in 2014, the very popular J. Cole, stumbles into the song with a sloppy, simplistic flow and decidedly unromantic lyrics. “Dick so big it’s like a foot is in yo’ mouth/And ya ain’t babysitting, but my kids are on yo’ couch” won’t win Cole any Grammys, but it makes a strong case that we could use a hip-hop version of the Bad Sex Awards.

A similar dynamic plays out in Miguel’s single “Coffee,” which was released on SoundCloud at the top of the year as a solo track, before a remix featuring Wale was more recently promoted to radio. Miguel treads lightly with “coffee in the morning” as a sly euphemism for wake up sex, and then Wale barges in comparing his dick to a scone. Wale and J. Cole are, let’s remember, considered two of the most forward-thinking and woman-friendly stars in mainstream rap. But they get on a perfectly good R&B song and spit embarrassing, amateurish sex punchlines, either because they think that’s what the track demands, or because they don’t treat a 16 on an R&B single as worthy of their best work.

When the shoe is on the other foot, do Jeremih and Miguel phone it in? The hits that Jeremih has generated in the past year alone for Wale, DJ Khaled, Lil Durk, and French Montana would suggest that he doesn’t. And Miguel has never sounded less than fully committed to singing his heart out on singles by Wale, J. Cole, and Ludacris. Of the short list of rappers routinely called upon to guest on other artists’ singles, only Nicki Minaj seems to give half a damn about giving R&B singers a good verse.

Everywhere you look, rappers and R&B singers are collaborating, and rappers are more often than not the weakest links. Chris Brown and Tyga’s Fan of a Fan: The Album highlighted the wide gap in the former’s R&B superstardom and the latter’s modest popularity as a rapper—it generated the lowest first-week sales of Brown’s career, but the best first-week sales of Tyga’s career. An aging Jay Z has been such a drag on recent Beyoncé songs like “Drunk in Love” that anticipation is low for the power couple’s long-rumored collaborative album. Nobody thinks B won’t give the project her all, but Jay has phoned in most of their duets since “Crazy in Love.” Industry puppets like Kid Ink rely on singers like Chris Brown and Usher to help them turn singles with bland, interchangeable rap verses into tuneful, memorable hits.

It seems like the industry has begun to notice diminishing returns on rap/R&B collaborations. R&B acts like Omarion, Jamie Foxx, and Sevyn Streeter have turned to a fellow singer, Chris Brown, to lend starpower to their latest hits instead of a rapper. Drake and Future, two major rap stars who have been lauded for the melody and emotion of their music, have released some of their darkest, most aggressive hip-hop to date on their 2015 mixtapes, and collaborate far less with R&B singers than they used to. Some of rap’s latest breakout stars, like Fetty Wap and Dej Loaf, have a way with melody, but it remains to be seen if they’ll keep the hits coming.

Mainstream rap has always had an uneasy alliance with R&B, born more out of commercial necessity than creative inspiration. The overwhelming majority of radio airplay for hip-hop is on stations where it shares playlist space with R&B—plenty of R&B stations play no rap, but there are few pure hip-hop stations. Early fusions like New Jack Swing were expertly engineered for crossover appeal. With Mary J. Blige’s hip-hop soul and the Notorious B.I.G.’s smoothed-out gangsta rap, Sean “Puffy” Combs brought the two genres closer together from both ends, and created a formula that dominated black radio for two decades. When Combs created the rap/R&B trio Diddy-Dirty Money, its 2010 album, Last Train to Paris, was something like his thesis statement on the lengthy musical experiment. But in the years since then, the sound has grown increasingly stale.

Rap/R&B collaborations often get a derided, particularly from serious hip hop fans, but it’s undeniable how much great music we’ve gotten out of them. Meth and Mary, Akon and Young Jeezy, Nate Dogg and Warren G, and countless other duos have created classics together that they wouldn’t have been capable of separately. LL Cool J helped invent the hip-hop love song with “I Need Love,” and it paid great dividends for him for a couple decades. We can laugh at Ja Rule now, but there was a reason that thug love duets like “Put It on Me” and “I’m Real” made him a superstar.

MCs used to actually bring their A game on R&B collaborations. Big Pun’s “Still Not a Player” and Fabolous’ “Into You” are as dense with punchlines and internal rhymes as anything they ever wrote. Twista made a very successful career out of contrasting his freakish gift for high-speed rapping with slow grooves and soulful hooks. Back when Lil Wayne was the best rapper alive, he gave Lloyd and Bobby Valentino verses as good as anything from his own records.

Rappers who half-ass R&B collaborations serve to highlight the power imbalance between their respective genres at the moment. Hip-hop sales have taken a hit in the iTunes era, but R&B has taken a much bigger dip. Only superstars like Beyoncé​ and Justin Timberlake go platinum anymore, and Frank Ocean is just about the only newer act with so much as a gold album. T-Pain, who for a couple years kept the entire rap industry afloat with his ear for hit choruses, fell out of fashion as soon as rappers got comfortable doing their own singsong Auto-Tune hooks.

Since rappers are a slightly easier sell than singers in a struggling industry, singers who can make catchy, radio-friendly choruses are enlisted to do the heavy lifting for rappers like Kid Ink and B.o.B who don’t know how to write a hook themselves. Wale has enjoyed an impressive run of radio hits, but nearly all of them have been buoyed by R&B singers. And most of those singers have seen their albums indefinitely pushed back for months and even years, from newcomer Tiara Thomas to established stars like Usher and Jeremih. ScHoolboy Q’s pitifully lazy raps on his own biggest radio hit, “Studio,” are a bitter reminder that the singer who made the song a smash, BJ the Chicago Kid, has been in label limbo for years. Ty Dolla $ign’s major label album has been kicked around the Atlantic Records release schedule over and over even as he continues to write and appear on singles by half of the label’s roster.

The marriage between rap and R&B is shaky, but it doesn’t necessarily need a divorce. Kendrick Lamar’s To Pimp a Butterfly and Donnie Trumpet and the Social Experiment’s Surf are two of 2015’s best albums, and they each show bold, creative ways of combining top-shelf rapping with jazz, gospel, and funk. On those records, rappers engage with the roots of soul music instead of just having an A&R rep pair them up with whatever R&B starlet can help them make a hit. Even Snoop Dogg’s latest album, Bush, treads familiar “rhythm & gangsta” territory with Pharrell, but the album’s endless supply of cookout grooves feels like a natural, satisfying turn for Snoop, one of the few rap stars left who can remember R&B before hip-hop changed its DNA. Maybe hip-hop/R&B fusions need to find common ground in the distant past, or even the future, because at the present moment, they’re in a rut.

Al Shipley is a writer living in Maryland. Follow him @alshipley.