It's real work, but also dirty work.
>real work
It takes a lot of effort to build a brand, get the right camera, build up skills, market yourself, budget, deal with self-employment taxes, and do other business stuff. It takes a bit more skill than flipping on eBay, and people consider THAT real work.
>dirty work
The consent is dubious, as the worker may be financially desperate and not in a healthy place to sell themselves sexually. Additionally, consent may not be communicated properly, and the genuine passion needed for FRIES (freely-given, reversible, informed, enthusiastic, and specific) sex might be there. There's also no ToS in these businesses most of the time. You shouldn't enter a business-client relationship without necessary contracts and all. There may also be tax fraud. Additionally, sex workers are the biggest self-promoters, and it's hard to find legitimate FWBs interactions in a sea of manipulative ass sex workers who pretend to want your cock only to try and sell you something. You also can't avoid them with adblockers, and they rarely ever pay for ads like most others have to do. And even then, it's not like people promoting their music on /mu/ are killing others' content, but sex workers drown out free users with their spammy garbage. Sex workers also often promote in kid-friendly spaces, like under viral tweets about animals, and borderline break obscenity laws.
So yes, sex work is a legitimate business, but it's scummy. Like fortune-telling and alternative medicine BS, but even more of a waste to society, and far more of an active nuisance. Sex and porn should be passionate and authentic, not commercial spam brought right to Twitter as opposed to shitty porn sites. It's also hypocritical we say, "Silence, brand", to services that provide actually good stuff, but then defend sex workers with every ounce of our bodies. Sex workers are not your friends. They're not like the small business that feeds their community. They charge hours of hard minimum wage labor for what is usually just sexting or low-quality iPhone photos. Many are also findoms and exploit people with strange addictions for profit. Fuck sex workers. I don't agree they're sluts, but they should either post for free out of a love for exhibitionism or GTFO.