I think that it would only be a problem if they were expecting to see a finished project made out of what they gave you. It can't always happen. Iv' received a couple of really nice things this way, so it isn't always a bad thing.
I can relate to people asking if you want to do sewing or mending for them. I always turn this down even if they are offering to pay me and they usually aren't. To me quilting/sewing is a hobby that I do not want to turn into a job. If they don't want to do their own mending because they don't think it's fun, why do they think it would be fun for me?