I always wash a quilt when it's done - unless it's a special wall hanging or as I'm working on right now - a silk necktie quilt.
I have a cat who will search out any piece of fabric and lay on it. I've even caught her sleeping on TOP of my machine when I have a quilt draped over it.
I'm also not the best housekeeper (lol) so sometimes there are extra threads or dust hitchhiking on the quilt.
And I wash them so I can double check to make sure no seams have popped in the wash - so I can fix them before the quilt is gifted.