Vrondi parent
To make it super easy to use the same "program" on your smartphone/tablet/laptop/desktop, wherever you are. And/or to simultaneously share access to it with friends/family. Yes, you can all just point a local app at a data share instead (the old way), but many apps aren't available across all these platforms to even make this possible across iOS, OSX, Linux, Android, and Windows, so this often doesn't work for a group of more than two people.
> many apps aren't available across all these platforms to even make this possible across iOS, OSX, Linux, Android, and Windows,
Thanks to all the spying/telemetry in most of those platforms once you use your privacy protecting app on them you lose the advantage of your data being self-hosted in the first place.