Why?

Systems are simpler, and not requiring a network connection also makes them more performant.

You can /should use sockets with ppstgresql, and even your backend (app server).

Because of its simplicity and its stability. And it’s absolutely capable of replacing many “traditional” RDBMs from a performance perspective or data size capability standpoint.

I’m not claiming that sqlite is capable of delivering high performance on par, the reason is that so many applications don’t need more performance that what sqlite is capable of.