The shady world of Brave selling copyrighted data for AI training

You can turn these off. It's part of their crypto rewards system (you get occasional ads, some crypto and then some of it gets distributed back to the websites you vist most, or just the ones you select) so it's on by default. But you can easily opt out of this from settings.

I don't think this whole crypto system lifted off really, but it was a neat idea to reward web content creators and users, according to traffic and preferences.

That's like the whole point of brave though, you get "paid" (peanuts) for watching the ads

Those ads are the point of their business model. They show you ads, and repay you with tokens. You can gift those tokens to content creators or sell them on the market.

You can disable those, they can be set to some frequency per hour and you get paid brave attention tokens based on that

Not sure if you were aware but you are able yo turn that off.