In a way I'm really kind of glad that garters have stayed out of the mainstream popular pets. You almost never see them being mistreated at chain petstores, and as far as I'm aware there aren't any 'harmful' morphs (like spider BPs and Green Apple pacman frogs) that people still breed for because they sell.
That, and like Jeff said, people are breeding garters bc they love working with them, not bc they want to turn a profit.