Loki has already faced a variety of opponents on the Internet, and it wins consistently. The problem is that these human players have just pride, rather than money, at stake. In chess and checkers, you can go to a tournament, pay the entry fee, and play to see how good the program is. Poker is different because it's meaningless without money. Further improvements may make it worthwhile for Schaeffer to bring Loki to Las Vegas.
Many technical problems have yet to be solved.
Moreover, the sorts of expenses associated with a trip to Las Vegas aren't normally covered by a research grant. It's not like you're hauling off wheelbarrows of money all the time. It's an accumulation over time. The lifestyle associated with the game isn't particularly appealing to Billings. He knows that if he were to play in Las Vegas casinos, for example, where the financial rewards can be much greater, he would have to improve his game considerably without a guarantee of an increase in income.