That’s crazy

Also, if I create a new account, I can't eventually log in with my old one... It's absurd

Don’t understand. So what’s the benefit to use it?

Idk...

I guess a benefit is that if you lose your private key @npub1earn...ja5j can restore it for you? From other comments below I see that @fiatjaf sees custodial clients as a way to "keep everybody in check"