They are leaving money on the table. More than that, they have funded deliberate efforts to find out the non-conforming site and kick them out of their network

They are leaving money on the table. More than that, they have funded deliberate efforts to find out the non-conforming site and kick them out of their network and that's not free. It's a deliberate, active decision and its cost. That's policy. Prioritized over cost and profit. In the US, there is often concern that the more valuable clients or end-users might otherwise boycot their product, or get them regulated even further. A concern that their are under pressure to do that, or else face even more costly consequences. (And they are. It's a very vocal part of society that's puritan.)