why some sportsbooks restrict certain countries but not others

I keep noticing that some sportsbooks just straight-up ban users from specific countries but let others sign up like nothing. I get it if a place is on some official blacklist, but I see lots of random exclusions. Sometimes it’s whole regions with no clear regulation issue, and other times one site lets everyone from Europe except like, Portugal or something. Always seemed inconsistent to me. Even some of the crypto-focused books pull this stuff, and those are supposed to be less picky about geography.

Is it really all down to licensing and legal pressure or are there other reasons they’d shut out certain countries? Maybe too many chargebacks or fraud from a place? Anyone have insight if this is based on data, regulation, or just operators being paranoid? Kind of makes it hard to stay reliable when books keep moving the goalposts.