I don’t know about all sites, but at some you aren’t playing against a computer. You are playing against other players. For instance, you might join a 9 player tournament. Suppose that this tournament each player puts up $6.50 to enter. The fifty cents represents what the house gets. Thus, the house gets $4.50 for the tournament. The six dollars goes into a pool of 54 dollars. 27 dollars goes to first place, about 18 dollars goes to second place, and 9 dollars goes to third place. The house could care less who wins, because the house has already won.