Has it ever occured to you that those abuses happen because of people's attempts to delegitimize it? Despite attempts to make it illegal or to otherwise shame those who participate in it, it hasn't ceased to exist for as long as humanity has existed. Prohibition didn't make people stop drinking alcohol, it just created more crime and unsafe scenarios. Drug use being illegal doesn't stop overdose. The fentanyl crisis is a direct result of drugs only being available from non-legitimate sources. Onlyfans has created a very safe space for sex work. It's not perfect but it is leaps and bounds better than an alternative where it is illegal.
I believe your experience that everyone you met on the streets found it to be degrading. Have you ever thought that was because of the environment that you were in? Sex work performed by homeless people usually only exists because no legal alternative exists for their clients. Also it becomes a last resort for income for desperate people and as a result can put them in not safe scenarios.
As far as it being degrading, that's also attributed to the unsafe conditions that many women and men are forced to work under. It really isn't hard to find sex workers who are proud of their life style and live happy lives due to their success in the industry. Unfortunately they are in the minority because of all of my previous points listed. Most of the negatives that you talk about are a direct result of your and others shaming, not anything that is inherently wrong or immoral with sex work itself.
I think the difference with his guitar playing and drawing was that he probably just didn't enjoy learning guitar. Tons of people buy an instrument to only learn later that they didn't like it as much as they thought. Not trying to say you don't know your kid, just pointing out that learning an art requires an interest to put into it. It can definitely be frustrating to realize that you aren't as interested in the learning process of something you had dreams of being good at.