It's a state's issue. Like marriage laws and regulations. They choose to either regulate and allow certain types of gaming (lotteries, horseys, and injun casinos) or exclude any and all. Here in Arkansas we embrace the ponies. OOOh that gambling is so evil.....unless you come on down to Oaklawn and lose your paycheck to us. LOL
These all techincally require the folks to be physically present within the jurisdiction (excepting the OTB deal). Clearly the federal govt nor the overwhelming majority of states (all but 2 have some form of legal wagering) are NOT anti-gambling, or there'd be no lotteries, no ponies, and no damn ripoff Injun casinos.
The methods that get the politicians the greatest kickbacks and returns are preferred and allowed.
Betting over the phone and "cable" falls under Interstate commerce, hence this is where the Feds kick in.