To answer some of your interrogations (though you answered some yourself) I’d say this:
First, to be famous, rich and powerful under a male supremacy you have to play by men’s rules. That means that the power you’ve gained can be taken away if you stop following these rules. It’s borrowed power if you will. Yes, they have the freedom to say no, but if they want to stay famous, wealthy and trendy, they have to please men.
In the entertainment industry, popularity is key. Since men own most of the world's wealth, industries and medias, they can decide what's popular, they create the trends, not women. So if pornography and sexism are popular then your job depends on riding that wave.
The more powerful a woman is, the more women in general gain power, the more men require of us acts of submission and contrition, to make sure we’re not threatening their supremacy. In this pornified and image saturated culture, these acts rely on self objectification mostly, as well as shocking obscenity. That's how you end up with Lady Gaga joining a gala in a big dress only to take it off and pose in her underwear as if on a porn set. In the middle of men fully clothed and laughing.
Women whose income depends on going viral have to do this the most: reality TV stars, models, pop singers and the like. And by “this” I mean wearing outrageous clothing, doing degrading things, staging scandals, imitating pornography, etc. Because their fanbase, and the current cultural climate, is frivolous. It’s tabloid culture on steroids.
Second, the objectification of these women’s bodies was always part of the deal when they started gaining fame. You think Rihanna’s success depends on her talent? You think if Beyonce was fat, butch and unattractive she’d be where she is now? You think any of the women here were chosen only for their talent? No. Their sex appeal is most of what we’re sold. Their talent, whatever it is, acting, singing, performing, speaking, hosting, comes second to their attractiveness according to men. That’s why on talent shows you end up with half of the judge pannel composed of ugly old men and the other half of young (or bottox filled) hypersexualized women.
Third, when you say maybe “there is a contractual enforcement”, the answer is yes, there is. It’s all product placement. Celebrities willing to remain so no matter what become puppets. That video of Paris Hilton and Jimmy Fallon pretending to be excited to have bought a NFT, a picture of a cartoon monkey, is the best demonstration of (failed) product placement via celebrities. You can see the strings so clearly it hurts. Go watch it if you haven't.
What they wear is often chosen by their stylists, managers, companies, producers, even their day to day clothes, especially if paparazzis are around. Brands pay celebrities to wear their clothing lines and promote their products. I find it especially obvious in Kpop. All of the sudden you’ll see all the idols of the same company wear the same brand, or even the same shirt, that’s because they are advertising these products as part of their contract. That’s why on the red carpet journalists are ordered to ask “who are you wearing?” and the celebrity (usually a woman) has to name the brand or creator. That’s not small talk, that’s advertisement, product placement. Same reason celebrities are invited to specific parties or fashion shows. Same reason they make specific posts on social media. It’s business masquerading as entertainment or personal choices.
So if the current most powerful trends are dictated by pornography, women are gonna have to wear pornographic outfits and act like prostituted women if they want to keep their jobs and sell whatever they have to sell. And the fact that even the most famous, wealthy and powerful women end up in this position is a clear indicator of the state of women's freedom as a whole.
Some women do decide to stop following men's rules, like Alicia Keys who stopped wearing make up or Kesha who called out her rapist producer, but it's rare and not without a cost career wise. A woman like Beyonce, who has been exploited by the music industry since she was a minor, knows nothing else really. As strong as she appears, she's really going above and beyond to satisfy men and I don't expect her to change. Same goes for most "empowered" and "fierce" female celebrities. Crawling for male approval is not a sign of freedom or power. The patriarchy would not allow them to take the stage if they were actually willing to challenge the status quo. So basically yes they could refuse to engage in this, but in doing so they'd have to relinquish the hard-earned power they borrowed. Most don't want to.
