Problem is, that if you can't pool accrued stakes across State lines, there's not enough liquidity to operate a viable online gambling business (see Powerball, etc).
Core players provide most of the liquidity and the cohort of core online gamblers is pretty small - circa <20% of total players provide circa >80% of revenue.
It's not like the State Lotto, where a large player base spend a couple of dollars a week; although Scratchcards similarly rely on a core player base as above.