Cabbagepatchkid, I am the same way. It was drilled into our heads in school....
I always prewash (except for charm packs and such) the reason is the fading and shrinking. I always get more fabric than I need.
I was not going to wash on a batik and decided I would by hand and oh the dye that came out. I would have ruined the whole quilt....
Do as you wish but I prewash...