BuyMeACoffee seems to be a service based on an extremely flawed premise: that of exchanging money for nothing tangible in return. That is normally known as a "donation", but this is not charitable giving; this is more like tipping. But even tipping is customarily associated with receiving some kind of service in the first place. This is more like tossing $2 bills at a stripper in a dark room, but 3,000 miles away.
Now most of these buttons were traditionally labeled "Buy Me a Beer" and I found them oftentimes on the web pages of starving F/OSS authors. The hackers would definitely be seeking to monetize their free and open-source software by any means necessary. It certainly stood to reason that they deserved a beer (or a coffee) for fixing bugs or simply providing a nice app to me that does something I want. Fair's fair. [Let's not forget that alcohol and caffeine are drugs, though!]
But essentially, if BuyMeACoffee is a payment platform that's disconnected from any tangible product or service being received, it could be warped to any use at all. Can I buy you a coffee if you show me one boob please? Can I buy you a coffee if you unalive my boss? Oh look, a package of (ammunition|fentanyl|CSAM) has arrived on our doorstep, let me buy you ten kilos of coffee to celebrate this unrelated event?
So I think that typically for capitalism to work, we should be scrupulous about correlating goods and services received to the monetary transactions we make for them. Or we should establish a good way to at least correlate a "creator" of software or content with the in-kind payments of "coffees" that they'll receive for actually doing work. Because if this is not properly regulated, we really do end up supporting a lot of shady stuff.
Who knows if we're buying coffee for terrorist cells or a human trafficking ring. I really feel like coffee money can be better spent on legitimate businesses with aboveboard ways of making transactions for tangible things. Sorry if I am being a real stick-in-the-mud about this, but this seems to be the main issue for regulators and law enforcement, and we need to admit that it's not an ideal way to do business.