sadly, it does happen.
I bought Abby from people who told me their daughter was allergic. I'm pretty positive that they got rid of her because they knew she was sick and would die sooner rather than later.
I rescued Otis from people who kept him chained outside for months on end with no food or water just because he tended to not know how to behave inside. And you know what? Sometimes he STILL doesn't know how to behave inside. But that's his previous owners fault.
Financed, paid cash or put on an Amex card, we can't assume ANYONE will be a fit owner. So maybe educating folks before they spend their money isn't such a bad idea.