Being asked to make a quilt for someone is a minefield, especially if it's a family member. When I started quilting I soon realized that everyone thought I was in the bedspread making business and that it would be less expensive for little teenaged me to make them a quilt than for them to buy a bedspread at Sears. Fortunately, I'd had a bad experience selling stuff on consignment at the age of 14 and I learned to say that I didn't make quilts for anyone specifically because then I'd have to make them for everyone who asked. However, if they'd like to purchase a quilt I'd already made they were welcome to do so. It was my Dad's idea to pin a price tag to each one. Once they saw the prices, (which were actually quite reasonable, considering), they never asked again.
I think each quilter has to decide what works for them. I've worked in a creative field where I had to create designs in all different kinds of styles to suit different clients. I didn't mind doing it because it was my job. Quilting, however, is my passion, and I won't create quilts that don't satisfy me creatively and that I don't personally love. Frankly, no amount of money is worth spending the time making a quilt to suit someone else, if you don't really want to do it.
I guess that's what it really comes down to. If you don't want to do it, don't. You don't really need to give someone a reason. I still get asked occasionally and I always say, (with a big smile), that I'm flattered they'd ask, but I'm not interested in taking on any more projects. They don't ask again.