I think the fewer bumps fits with the preference for high alpine terrain. Spread everyone out instead of forcing people on to a cut trail and there will be fewer and smaller bumps. Whistler/Blackcomb has more alpine than anywhere in North America, so you can ski a lot of steep terrain there without huge bumps. Mammoth is the rough equivalent of 1 of those 2 mountains in alpine terrain. Squaw is probably the exception to this rule. It's wide open but gets bumped up more.
Colorado and Taos are mostly trails (except Vail's back bowls), thus more bumps. Same with Silver Star's Putnam Creek.
The other thing that holds down the bumps is low skier density. Alta and Snowbird are still fairly low density, though lift upgrading is bringing both closer to average. The upper reaches of Jackson and Big Sky and the other Canadian places are lower density than Alta/Snowbird or Mammoth.
Colorado and Taos are mostly trails (except Vail's back bowls), thus more bumps. Same with Silver Star's Putnam Creek.
The other thing that holds down the bumps is low skier density. Alta and Snowbird are still fairly low density, though lift upgrading is bringing both closer to average. The upper reaches of Jackson and Big Sky and the other Canadian places are lower density than Alta/Snowbird or Mammoth.