Call me Professor Pete, a partially rejuvenated professor of Psychology at a terrible tier 4 college in the West.
I read your recent call for posts about why we still teach, against all odds, despite the knowledge that the world of higher education has gone to pot, has become seedy and disingenous, has become as trite and boring as our own students seem to be.
Well I do it for three reasons:
1) It makes me feel like I'm doing some good. My students are mostly lousy, but in a class of 40-45, 2 or 3 end up surprising me. I get a visit around midterm from someone who wants to know what book I was talking about in class, or what study I referenced. I send that person on to another level of reading or understanding, and occasionally I take some dimwit and turn him/her into a Psych major. These kids sometimes go to grad school. Sometimes they become professors. And some of them end up being friends of mine. I know I've played a positive role in these people's lives. Even my worst students learn something about what it means to think, to study, to be responsible. A student who passes my class has had to achieve something. I think that achievement (even if you think it's relatively small in the grander scheme) helps that student in all future challenges.
2) It builds a continuing thread of information between the generation before me and the generation after. I believe in knowledge. I believe that there is information that needs to remain vital and interesting. When I teach the theories or ideas of a famous mind from an earlier decade or century, I'm casting it in all new light, in all new context. It's one thing. My teaching of it makes it a new thing. The understanding my students create is yet another new thing. It's alive. It changes, modifies. Sometimes I cock it up; sometimes I make it better. But it lives through me, and then goes on past me into the heads (or at least ears!) of my students. I believe that the information deserves to live on, and in teaching it, I keep it alive. I do it in my field, and I have many colleagues who do the same thing in theirs.
3) It makes me feel good. Selfishly, I love my discipline. If there was no shitty college with its low pay and heavy workload, I'd still read much of what I read each semester. I'd still debate the ideas from my classes with like-minded people (even if I had to find them on Friendster.com). It's a vocation for me, but it'd be an avocation, too. It blows my hair back, and I'm lucky enough to have found something that makes me happy that I also can get a few ducats for.
Maybe those reasons aren't high-falutin enough, but they got me through the summer.
Now, out of the jams, and back into my Dockers!