Honest answer: they are hard to use.
When I first got involved in bitcoin in 2019ish, I looked at bisq - but was not able to have a computer on for extended perioids of time. Also, I had no bitcoin to start with.
Then i did an account to "localcrypto.com'. After a few unsuccesful bitcoin buy attempts and continuos email spam, I gave up on that.
Eventually I had to surrender my privacy to CB. Even there I have the problem that fiat only moves 8h a day in five days.
Robosats is an interesting one. The problem is however, is not with BTC but with the fiat movement. How to do it so that my bank does not suspend me for money laundering.