The artists you mentioned get played on KCRW...they just tend to be played on some of the late night shows. For example, Tricia Halloran, who hosts "brave New World" on Saturday nights focuses on Guitar Rock and I have heard her play some of the artists you mention. ANd I have heard Crosby, Stills and Nash on MBE and Nic played the Beach Boys just the other day.
The other factor is most of the shows follow the MBE mantra of "New, Upcoming, and Recent releases" so 3/4 of what they play is things released withthin the past 3 months. Eric J. Lawrence, the host of "Dragnet" also has a very "college-radio" themed show and is definitely worth checking out. As a rule they don't play an excess of commercially succesful artist...yes they will play Bjork, Sigur Ross, Jurrasic 5 and such...but household names like some of the ones you mention, or Madonna, Sheryl Crow, U2 and such...not as often.
I wish there were more specialty shows as there had been in the past...but apprently the audience hasn't been as significant enough. I always thought with a seperate on-line feature they could bring back some of these specialty shows.