A studio helps them get started. We're cam watchers so we're familiar with what would be needed to start but someone not familiar would probably not even know where to start. They'd need a good enough computer, toys, lighting, good internet, vpn, know which sites to sign up for and what to do. Plus some of them wouldn't speak english or be confident in their level so the studio has mods to help them communicate. You go to a studio they set up everything for you, get all your docs verified, train you, etc you just have to show up and stream.
And even if they know all of this info a computer and toys are expensive and I assume most wouldn't be able to afford it when starting out. Alot of them probably also live with their parents so they can't stream at home.
The last thing I can think of is that it probably also gives a sense of safety and legitimacy since that work can be illegal in some countries.
For aya specifically though idk. Maybe she made enough and is happy to quit. Some girls just want to earn some extra money in the short term then work a regular job rather than wanting to cam long term.