Considering a lot of college towns are right next to, or within large metropolitan areas, yes, a LOT of people are commuting in these days - Every school you mentioned in fact, is seeing this trend.
UW? So many kids from Tacoma, Olympia, and Everett areas shuttle in there every day... Not to mention those who don't actually live in Montlake. Housing costs, the economy, and the fact that it's a shitload cheaper to do rather than live on campus is definitely something that parents are considering even more these days.
UC Davis? It's only 20 minutes from Sacramento. I know at least 30-35 people who have lived at home, or in cheaper confines on the other side of the river, or home in Vacaville/whatever, and commuted into Davis for classes. Hell. My brother carpools with a friend of his every day from my folks' place to campus... and he carpools in with 3 or 4 people depending on the day. You figure it out and if it works, it works.
Eastern is a similar situation. It's right next to a metro area of over half a million people... and its about 20 mins from downtown Spokane. Of course people are going to live at home and commute in just like the two you mentioned.
You'd be surprised with how many kids these days are commuting from home. Especially in California, but elsewhere too. I don't actually have the article in front of me, but I was reading something a few months ago in the Portland Tribune talking about how, especially 2nd year college students at Portland State, have been heading home for their 2nd year and commuting in for school to save money, rather than paying the costs of living on campus, or the higher housing costs in Portland itself. Figures were somewhere in the 50-55% range of undergrads.
So, perhaps its not "most everyone" but it's a lot more than you probably would think.