The variance is also what allows poker to thrive and pro players to have an income though. Since poker is zero sum (really negative because of the casino's take) there has to be a steady supply of losing money playing. That means bad players have to believe they have a shot. If they never or very rarely won against higher skilled players, they'd dry up.

Imagine casinos that had cash chess tables or basketball courts. Would you have enough dead money willing to risk playing? I'd wager no. You'd get occasional fish willing to try but they'd get dunked on and go home. Without enough new money, the game would dry up as the best players and the casino accumulate all the rest.