Because it's sitting in their account and they don't care.
If you as someone selling things decided to take BTC / crypto thought PayPal since you were using them to take payments anyway and it was nothing more then a few mouse clicks but you don't care about BTC / crypto then you could easily wind up with some in your account. Now you have to give the DMV money, and you can now spend on something you were going to have to spend money on anyway. Yes, there is a fee, but 'whatever' you no longer have to worry about this BTC / crypto sitting in your account.
THAT is PayPal's target audience. Fees in, fees out, terrible exchange rate. But, it's a painless process.
I have a few clients who STILL use PayPal just for credit card processing. They could save a bunch my moving to another vendor. But over the years they have integrated PayPal with so many things. Even saving 2% on the $300000 (so $6000 net) they move through them every year will cost them more in redoing their back end then a few years of fees.
-Dave