I think the reason is because that really didn't work for some reason. Starbucks experimented that idea for a while. (I think it was something like 3 hours for buying a something using registered card, and that then they decided to open it up...)

My personal opinion about MAC address filtering though, if they become the norm, everyone will start using a piece of software that changes MAC address periodically... (As it's already trivial to change your MAC address...)