That’s not a question for actors; it’s a question for producers and directors. Fanning did not literally take the role from a trans actor, because it was not offered to a trans actor. Fanning was brought to the project by the film’s producers and creative team, because she is marketable following the box-office success of Maleficent, and because she’s an extraordinary performer with a proven track record in art house films like Ginger & Rosa. She likely agreed not because of the paycheck, but because the role would offer an exciting acting challenge and the chance to work with other great actors.

Films like Three Generations are also potential award-winners or, less charitably, Oscar-bait—a genre of cinema with its own economics and politics. Playing a trans character is one of many roles that actors seek out for a big career payoff via industry recognition. Physically transforming for a role, like gaining or losing weight, or becoming unrecognizable through makeup and effects, is a tried-and-true way to generate awards buzz. Playing trans worked for Hilary Swank in Boys Don’t Cry, Lee Pace in Soldier’s Girl, and Jared Leto in Dallas Buyers Club, to name a few roles that garnered acclaim. Harvey Weinstein snapped up Transamerica as one of the first features under the Weinstein Company banner after correctly betting that the film would become a big award-winner. Weinstein himself said he didn't recognize star Felicity Huffman for the first 15 minutes that her trans character Bree appeared on screen.

Developing a film or series requires not only investing money, but also time: Producing Dallas Buyers Club took 14 years from concept to screen. Actors for the major roles were shuffled around until the last went to Jared Leto, who replaced Gael Garcia Bernal just prior to filming. Leto is exponentially more famous than the most well-known trans performers, and he’s had the chance to demonstrate his talent in many well-regarded films. He also has a huge global audience of young fans for his band Thirty Seconds to Mars. No trans actor has his level of experience and name recognition, so the gender-fluid character Rayon went to Leto after all the time and energy it took to get the film to production. This long and torturous road to completion is quite common, and casting is often a game of musical chairs as schedules change and other acting opportunities emerge.

As the saying goes, it’s not called “show friends,” it’s show business. Trans issues were considered so edgy and unbankable just a few years ago that even Ryan Murphy, creator of hit TV shows Nip/Tuck, Glee, and American Horror Story, could not get a trans-centered series to air. Originally saddled with the cringe-worthy title 4 Oz. (referring to the purported average weight of a penis), Murphy’s pilot centered on a sports writer who transitions to female. After a real transgender sports writer “detransitioned” back to living as male and later committed suicide, Murphy’s main character was changed to a gynecologist, but the most they could get on air was an unsold pilot released as a TV movie called Pretty/Handsome. The gynecologist was played by veteran non-trans actor Joseph Fiennes, but even with a known lead, the project failed just as many other trans-themed projects had over the years, most of which never even made it to pilot season.