[notouch]

Slansky's 'The Theory of Poker' tells it best. You can calculate probability and odds playing poker much more precisely than you can trading. For each hand you hold you know (or can calculate) the exact probability of that hand winning. You can also calculate your exact odds on each bet you make because you know how much you stand to win if you have the best hand and how much money you need to bet to continue. Therefore if your probability of winning is higher than the odds you need to pay to continue then you should bet. Of course in reality there's the issue of bluffing and gamesmanship but these apply less to online poker.