From my understanding it has to do with the legalization of online gambling in certain states. It's probably up to the individual book whether they can operate in a certain state
Pretty much this.
Combination of states who have shown they will be very litigious of someone doesn’t voluntarily exclude its residents from playing there vs the licensed operators and in cases like Nevada - the number of pro players and potential for drawing in “undesirable” customers for the book.
Nevada is very protective of the well established casinos and every politician is in their hip pockets. No way in hell they aren’t going to fight like hell against an offshore operator who has a fraction of the overhead (including political payoffs).
NY is another very litigious government - these guys see what the fentanyl seizures and Purdue Pharma settlements handed out by the courts and want no part of that - easier to exclude than risk pissing off certain states.
You’ll notice Florida and Texas are not on the offshore banned list as far as I know - despite being very protective of their licensees - probably coming towards a showdown in the next 5 years as the apps lose more and more and customer cost of acquisition increases.