Is it almost customary that one should put on a spring seat whenever you switch from shocks to rigids? just curious and I really don't care about a bumpy ride (although I do live in PA and our roads are crap)...

 

Nah, the spring seats are just to try and give some extra comfort after shocks are removed. And some people prefer the look.
But some people also prefer the look of a low slung seat better.

 

you can ride it without springs on the seat if you put rigids on it but why? the little bit of spring has to help so why not? you'll be stopping for a kidney break a little more often without the springs that's all.