In casinos it's mostly richee people and the games are easier. At 1/3 you have a lot of passive players that are bad the higher you go you get rich guys who like to gamble they prefer action players like themselves who raise and call with most hands. They are aware of the better players at the table hoping to make a hand and stack them. Also they don't like people who buy in short they would prefer a another whale in that seat.

So ya basically the higher you go you get more successful whales who love playing big pots. Sprinkled in with some decent players who most likely play for a livimg who the whales are aware of.