Thing is, a large percentage of internet-connected users might have two or more devices. The simplicity offered by a cloud (be it hosted or selfhosted) password manager is a huge benefit.

And unless you’re already running a syncthing-like service for something else, setting it up just for a password manager when other services provide it out of the box, is not worth the hassle usually.

IMO Keepass and Bitwarden aren’t exactly the same, as the latter has cross-device sync built-in.