In America, net gambling is illegal by federal law. You can't gamble down telephone wires and that's where the digitized pulse travels. But the web is world wide. They can suck money out of plastic with no problem at all. And they pay no tax.
Overheads are minimal.
No need for all that expensive Las Vegas glitz. Washington is powerless to control them, any more than it can control the Central American drug cartels. It's the poor, uneducated, lonely and elderly who are most susceptible. The nice old lady who would once enjoy a cheap night of bingo can now max out her credit cards in half an hour. But not one of the million who gamble every day has been prosecuted.