I wash all the quilts I make for give away or missionary quilts and I wash all family quilts. If I don't want the old-timey look, I choose a different batting and always preshrink.
And I prewash fabrics because some run no matter what you soak them in first.
But, for custom quilts, I do not wash (I don't use starch in piecing). I do clean up though with a lint roller, etc. and I always give washing instructions. And, I always ask if they want me to wash it first. Most do not. They are paying for a new quilt and want it to look that way.
So...different strokes for different folks. Do what works best for you.