It's true: Many of us LA quilters don't like using sheets.
The weave, even on the looser woven ones, don't 'heal' as well in the event we need to pull stitches. The needle break the threads in the weave instead of going between the threads. We're not perfect, and can't always hit the exact same holes. I've also found on sheets that I've purchased for my beds, that some of the less expensive sheets - those with the lower thread count - also pill after a few uses/washings. I'd hate to put that much time, money, and effort into a quilt to have the back pill or have thread breakage holes that don't heal.
I have a couple of customers that buy flannel sheets and those work great. If you watch the sales at some of the better stores, you can buy just the tops for a great price.