it does snow in california, just not in places like l.a., san francisco, or san diego...
if you live in/near lake tahoe or yosemite, it definitely snows...
i don't see sorels as being a trend...they're functional...
i had a pair when i lived on the east coast 10 years ago, mainly because in all the snow/rain they keep your feet warm, your ankles are protected from sprains, and the treads on the bottom keep you from slipping on the ice (unlike l.l. bean duck boots)...
i think the reason they have gotten "trendy" is because companies like urban outfitters and j.crew are styling with them in their catalogs, but east coasters (and others that live in colder climates) know they are a functional necessity...