I know that some pin and a lot, me not so much, actually really not at all, not to hold my pieces anyway, I sometimes use them to mark the side I am to sew.
It is a personal thing, some have to, some don't, I wouldn't quilt if I had to pin. though I have sewn for more than 15 years, makes a difference in my style of quilting, do what you need to do to be comfortable, if you feel the need to pin, pin away. would my work be more acurate if I pinned, maybe, maybe not.