I agree with your premise, I think. These agreements are about companies agreeing not to send recruiters INTO THE OFFICES of other companies... that's just crappy business. In fact, at the peak of these booms, companies get into departmental "retaliation" where one person leaves then gets back at their former boss by hiring away co-workers and causing projects to be delayed. That's what was going on at the time and these companies wanted it stopped.
I think that companies were just agreeing to stop accepting recruiters soliciting from other big companies. In my book that's fair. I've been at offices where the same overzealous recruiter calls every damn extension because they got the company phone list... it's really disruptive and only sews distrust between the remaining employees. If companies want to use another channel like referrals or taking non-solicited applications I'm all for that.
the other thing of course is that California doesn't respect even limited non-compete agreements. While the buddies in Seattle DO PUNISH their former employees for "cheating" on them. If California would enforce limited non-competes (as well as say yearly contract terms... like apartment leases) then a lot of these issues would never have been issues in the first place.