I wash my fabrics to make sure they are preshrunk and color fast. If I happen to buy precuts, which is not often, they do not get washed. To wash or not to wash is a personal choice and I will not tell someone they are wrong if they choose not to, just as I don't want someone to tell me I am wrong for prewashing.
Yes JulieR I have noticed how "twichy" people get over this topic!