Canadian Avalnche center is trying to explain it as - snowmobiling is a new sport and they don't have the 100years of experience of skiers.

Bull***t - snowmobilers like concave slopes to see how far up they can get. Avalanches like concave slopes because of physics.
Add in a few cans of beer and bingo - the perfect avalanche trigger.

* yes I know there are snowmobilers who only ever go at reasonable speed on marked trails and enjoy the sport as way of communing with nature - but none of them live in Alberta.

Whats worse is that every year they come to BC and as a result we get perfectly safe trails closed to snowshoes because of avalanche risk. The only risk being that if some idiot drove a snowmobiler up it there might be an avalanche.