What do the Samsung Galaxy Note 3, LG G2, Moto X, HTC 8X and Apple iPhone have that Nokia's gorgeous Lumia 1020 and 1520 don't? They aren't shackled to AT&T.

Nokia announced its 1520 phablet today, and it will be America's only Windows Phone phablet. The now three-year-old platform is growing, and U.S. carriers have said that Windows Phone is their bulwark against being yanked around by Apple and Google.

Yet Nokia can't seem to get its flagship phones onto multiple carriers. Look at the Lumia 900, Lumia 920, and most importantly the 41-megapixel Lumia 1020, all AT&T exclusives. Nokia is the only major manufacturer having this problem with its flagship phones anymore, and it's a weakness that Nokia and Microsoft will have to overcome if it is going to really compete in the U.S.

Carriers and manufacturers used to have a deal. The carriers would only accept exclusive or customized phones, but they'd take over the marketing. Nokia did poorly in that regime because it was used to selling the same models worldwide, but Samsung, which can churn out many customized models, really flourished.

But first the iPhone, and then the Galaxy S III changed the game in the U.S. Carriers grew to accept that flagship phones would appear on several carriers with only light customizations, in exchange for the manufacturers shouldering marketing costs. While there are still some carrier-exclusive phones, only Verizon puts real muscle into marketing them anymore, and even that's beginning to fade. We're not seeing the oomph behind the most recent range of Droids that we saw with previous generations. Other carrier exclusives tend to get a four-to-six week window at the front of carrier stores, after which they're replaced by the next new hotness.

Nokia can permute its phones to get them onto various carriers, but all that customization dilutes its marketing abilities. Pairing the AT&T 1520 with a Verizon-exclusive, rumored "Lumia 929" phablet is a 2007-era strategy. Consumers now want to hold one model in their heads, not wade through a mess of similar-but-different phones.

AT&T: Nokia's Bad Boyfriend

Nokia has a long history with AT&T, but AT&T hasn't been good to Nokia. AT&T keeps getting Nokia exclusives, but keeps selling lots of iPhones and Android devices. At one point, 80 percent of AT&T's smartphone sales were iPhones. Although AT&T didn't reveal the sales mix in its most recent quarterly results, it was about two-thirds iPhones in the previous quarter, and this quarter the company's CEO called out a lot of Android sales in his earnings conference call.

Nokia, meanwhile, can't get any traction. In its Q2 2013 results, it only shipped 500,000 units in the U.S., a decline from the previous year. Its exclusive deal with AT&T for its 41-megapixel Lumia 1020 doesn't seem to be doing any good, so why return to the well for the 1520?

Back in Nokia's heyday, AT&T was the only carrier whose radio technology and frequency bands worked well with Nokia's global phone lineup. So it was easy for Nokia to customize its phones for AT&T; back in the days of exclusives, that was a no-brainer.

But that relationship has long outlived its usefulness. The new Qualcomm chipsets being used by Nokia, LG, Samsung, and Apple can be configured to work with any of the major U.S. networks. Nokia knows that; it's offering the 2520 tablet on AT&T and Verizon. Unfortunately, the 2520 won't sell because it runs the confusing Windows RT, not the powerful Windows 8.1 or the sleek Windows Phone OS. The 1520, not the 2520, should be Nokia's holiday star.

Ultimately, this all comes down to influence, and Nokia's seems to still be near zero. The company has less juice with U.S. carriers than even HTC and LG, which have managed to get the HTC One and LG G2 out on all four major networks. Solving this problem should be Job One for someone at Microsoft as soon as the company properly ingests Nokia. If Windows Phone is going to succeed, every American on every carrier needs to be able to get the best Windows Phone possible. AT&T exclusivity needs to end.

For more, check out PCMag's Hands On With the Nokia 1520, 1320, and 2520 and the slideshow above.

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