Why do mid-high stakes games exist?

[iversonian]

I'm a 6-12 player. When I see a 20-40 game, for the most part, I see notice that the players are basically competent, and that they could probably beat the 6-12. Now, at that 20-40 table, there are some players that are not playing with an edge. Why is it that they play the 20-40 instead of a lower limit? This applies to higher stakes players as well. The 3-6 and 6-12 players, they're just looking for some diversion from daily life and lose a couple hundred bucks at the tables, no big deal. But folks playing 20-40 are, I would imagine, smart enough to realize that losing money, when they could be winning it instead, is kinda stupid. What is a typical personal profile of a losing 20-40 player?