YES!, I just about know why also, it's because you can go to some stores, and buy hand quilted quilts for as little as $15.00 around here. I don't know where they are getting the fabric, and getting it hand quilted, and make any money off of a quilt for that price. I went to a craft show, and there were two ladies selling these $15.00 quilts for $65.00 a piece. I know they were from that store, because they still had them in the bags that they came from the store in. The quilts were the same colors, same patterns, and every thing.
So, to answer your question, I know that people do not know how much time and money is put into a homemade quilt, or any item for that matter.
The only people that knows are true quilters like you and me. I am sorry that it keeps happening to you, did you tell every one that you made the quilts? If you didn't, maybe they thought that you bought the quilts.
I made my daughter a quilt for her wedding, and when I asked her if they were enjoying the quilt, she told me she was afaid it would get messed up. She told me it is still in the bag in a closet. I told her it was made for them to use. Oh well, what can we do? Just keep making the quilts, just because we love doing it.