I am a tenured associate professor in 'hard science' at a major research institution (part of that cluster famous for the Ivy on the walls). I've been an associate professor for ~5 years.
Fairly recently, my chair asked about timetable for promotion. Said Chair fell to the floor (almost) when I replied "I could care squat about promotion to full professor". Seriously - who cares? There are two motivations I can think of for wanting promotion. (1) money, and/or (2) ego. I get paid more than enough in my current position, thank you very much, and anyone who thinks a different academic title means anything to anyone (other than their own inner ego) is delusional.
I'm an associate professor. I write 3-4 good solid papers a year (have about 60-70 so far, 2 books, and a bunch of book chapters), do my share of teaching, edit for a couple of journals, get grants when I feel like it, and supervise students if they're good and I feel like it. I shift research gears with some frequency, pursuing what interests me. I go to meetings if I feel like it, not as a career move. That, of course, is the point of tenure. I do what I want, more or less.
The university system is predicated on people striving for promotion, for 2 reasons. One, the bean counters and political types in the university administration understand that outside of academics, like government agencies, alumni groups, and other folks who might have $$$ to give to the school, title carries gravitas. A lot of universities make a big deal out of the number of 'full professors'. Second, and more to the point, they want the lure of promotion to keep you active - not at anything as trivial as 'intellectual work', but...getting grants. Pure and simple. Without overhead off major grants, universities would crash and burn - so, how do you keep everyone motivated to keep playing the grant game? Hold out the lure of the 'perks' of being a full professor.
Problem is, the system doesn't account for people who could care less about money, or title. People who publish just fine without a lot of $$$ rolling in. People like me. I'm doing what I want to do now. I loathe administrative assignments, and if doing them is a necessary step on the road to 'full' title, I'll pass.