browned:
People don't buy internet services with the primary focus on breaching content right TOS. I think you will find it hard to prove the ISP's are benefitting from these services. I think customers benefit as they don't have to pay for overseas VPN services.
Heavily marketing it as a feature seems to suggest that the ISPs in question certainly believe it makes a different when choosing your ISP (or choosing to stay with your current ISP). That may or may not be true, but that's clearly why they'd do it.