I don't think it's necessary at all. Is it nice sometimes? Absolutely.
I tend to shave right after a hot shower. No prep, no Pre lather lather, just a couple of splashes of hot tap water and lather up, then shave away :). I try to be a minimalist (says the guy with 30 soaps/creams and 20 or so razors).
Everyone's face is different in what it needs. Refined technique does help though.