The thing about franchises is they're meant to be a cookie cutter business, not a place to cut corners or innovate. Sure it sucks to have your supplier be a monopoly, but you also have their support and vested interest in your success. If your store sucks, it reflects badly on the franchise. If every franchise goes off script and uses different stuff then you dilute your branding which hopefully is successful. It's like a sports team doing their own plays ignoring the coach.

Now, management and policies.. sure they could vary absolutely, and I can definitely see different stores having "unofficial" but enforced policies not shared with corporate.