Woody:
I scratchbuild ships, usually in wood but I'm well stuck into my first styrene ship, a 1:48 corvette.
Why?
Because the manufacturers don't make kits in my chosen subject and scale.
I do have some aircraft kits in 1:48 but again they are resin or vac-form because of the off beat subjects, so the kit bashing (scratchbuilding) is intensive.
As for the learning thing I am always flattered when someone comes back to me with the comment that my tip or whatever proved useful, and one main reason I joined this forum was to pick up on things the others are doing.
The keys to building from scratch is a good set of plans, patience and common sense. For many subjects, you'll have to work out your own plans. The satisfaction is unlike anything else in modeling when you have planned and engineered a successful model from nothing except bits of plastic sheet and assorted odds and ends.
I hope you pursue your builds, and please feel free to ask about things any time.
Reagrds,
Bruce