You know what I think it is, seriously. A lot of rescues are older. You don't necessarily know what you are getting. A lot of people want to train their dog the way they want. And you know the old saying, "Can't teach an old dog new tricks."
Also, people are afraid of abused dogs that might be vicious. My aunt is a prime example. She adopted a Yorkie, and he bit her, my cousin, and the vet! The vet said he should not have been adopted out because he's vicious.
So I said recently to my cousin: If you want a dog, let's get a rescue. "NO WAY!!! I don't want one like Bailey." I can understand what he means.
I would consider a rescue, though. But truthfully, I'm hesitant too.