Subway franchises can opt out of those coupons too.
I think the problem with Subway is with the low entry barrier to open a franchise. You got a bunch of people who's looking to open their first restaurant, so they gather up whatever they can find underneath their couch and hope to make it back in the short term. Then they'll count every single penny that walks out the store, including condiments.
With larger franchisees like McDonald's the requirements are a lot higher and it usually ends up where you got an investment group who owns them. These groups usually have first dibs on potential locations. Same deal with 7-eleven. Subway on the other hand I'm not sure. There was a time where I was seeing multiple subways near each other.