Because sometimes even criminals need to buy things that aren’t illegal, I guess. And the legitimate people who have those things don’t want to play games dealing with fake internet money.
If I want to buy a jetski, the place I buy it from isn’t going to take crypto because the people that sell the parts for it don’t take crypto and the people who build it can’t pay for food in crypto.
Crypto is only useful for rug pull scams, money laundering, and black-market transactions. It’s real innovation is undoing centuries of banking regulations so that people can learn the hard way why all those regulations exist.