I think this is something that should be handled on an individual basis. I know the ladies at my quilt shop would gladly hold whatever for me, but I'm in there just about every week. If I was a customer they didn't know well, or know at all, I wouldn't expect them to cut and hold fabric for me. Too easy for people that don't regularly shop there to not come and buy the fabric.
I'm surprised Walmart or Jo-Ann's would cut and hold fabric at all.