Also, exchanges don't ask you to pay taxes or What stops the company to maintain a team of people whose work is to register new wallets and accounts on exchanges all day every day? How exchange going to figure out that a certain person's account is linked to the company? Even if they will hire detectives, what will they do if there is a whole team with rotating people? Also, exchanges don't ask you to pay taxes or declare where you got money from, that happens after you take money from them to your fiat bank accounts.
So basically, set up a whole new, extra inaccessible payment system (that definately won't be intercepted by middle men) to be able to make transactions. And then how do you convert back to the dollar? You're in the same position.
There are countless exchanges, more than 2, and new ones can open every day (a big difference compared to payment processors, where just 2 basically monopolized the market).
There are countless payment processors and digital wallets, and new ones open regularly. You just don't hear about them (esspecially in North America) because unregulated capitalism has allowed Visa, Mastercard and PayPal to monopolize the market. What stops that from happening again?
Aside from what others are saying, I think you're also making a mistake in interpreting people's interest in generative AI. Most people making/using AI art aren't looking for "good art", they're looking for a "good enough asset" to fufill a niche they don't or can't value. For example, a small buisness owner might use AI to create their logo. It won't be good, but its only competing with what they can draw as a non-artist. It only needs to be passable, not good. Similarly, big buisnesses like it because it can create images to add visual flair, without the cost and personality of stock photos. In the same vein from the viewer perspective, they often aren't looking for something high-quality or thought provoking (esspecially on a platform like Tik-Tok). Generally, people scrolling on Tik-Tok aren't looking for something good, they're looking for something mindless to distract them, thus the emphasis on mindless scrolling over guided or curated content.