And that is the significant difference that decides who has the authority to regulate your gambling activities, and who's responsibility it is to enforce those regulations.
Another legitimate question: Who regulates the internet gambling site? Who assures that you won't get stiffed? Who makes sure the "software dealers/machines" aren't rigged?
States that allow gambling also have regulations and regulators in place to ensure a fair deal, both to protect the gambler and the house.
Such a state could be open to liability if their regulators fail to enforce state regulatory law upon internet gambling.