I'm not sure how much value that map has, as it lists only "Total Skiers/Boarders." Skiers/Boarders per capita would be a better measurement, imo.
I'm not surprised by the 7% skier population in SLC, though.
Hell, in Sandpoint, Schweitzer is adjacent to and clearly visible from town. It surprises me how many people most apparently) don't ski here despite that immediate proximity...just 10 miles up the road.
I know theres a big lake up there but what else do they do then its pretty remote im surprised theres not alot of skiing up there as well from what your saying.