> Safari is a minor browser by overall market share and is broadly standards-compliant.

It's officially compliant but in practice there's a lot of buggy implementations in Safari and you'll spend lots of time on workarounds and debugging.

It's also the last non-evergreen browser being tied to the OS so it's the slowest to update, compounding that effect.

> So then why aren't PWA's super-popular on Windows and on Android? Since Safari doesn't affect those?

Personally I think that's because it's still not that convenient even on Android even if better.