Exchanges and casinos block ips from the United States but everyone just uses a VPN, why even block their ips in the first place when you know they are going to do it anyways. I'm guessing they do it so they have some type of deniability?
Blocking certain Ip addresses where their services are aren't accepted is actually the best possible option that a certain company could do to defend their side when somebody will sue them especially the government in the near future.
Keeping their defense up will not be useless at all as it will be beneficial for them to be in the right track of respecting a certain laws from x country. Actually there are few legit gambling websites and most exchanges follows the KYC policy so they could easily identify the nationality and identity of the user. By doing the KYC policy it will be completely impossible for a certain user to use their service even if they are using VPN because their account verification request will surely gets rejected.