Gambling has a heavy association with criminality. By allowing open gambling we must also accept the externalities.

Or we could, you know, not legalize gambling.

I do not think it is so clear cut as legalize/not legalize. Current legislation often doesn't even consider this gambling - however, even if you took the viewpoint that making it illegal helps, you then have to accept the externalities that arise - crime rings will develop that offer the services, and now their users are criminals and completely vulnerable to any amount of bad/malicious practices there.

Which, historically, is a much smaller and easier problem than legalized, unregulated gambling.

We already have a model for this in the casino system.

Like sure, there’s some small black market here, but it’s relatively minuscule.