Well, a couple of reasons.

For every teaching low, there is also a teaching high. I got to orange pill my class once (#899199), and will continue to do so going forward. I've helped a number of students achieve their goal of going to grad school, or get jobs in nice firms. Overall, our school is very good at moving students up the socioeconomic ladder since most come from underserved and minority backgrounds.

I have to remind myself not to take the lack of engagement personally. A lot of these students work part time or even full time jobs, or have family to take care of. (Like I said, many of the students come from underprivileged backgrounds). It's hard for them to muster the energy to take class seriously. It makes teaching hard, and it probably means they're not learning a lot.... but I guess getting that degree is still better for them than not getting it, even if they don't learn much. So I guess I'm just a step on that ladder... and can I blame them for using me that way? I get paid for it after all.

And lastly, I can't deny that it's just a fairly cushy job. It doesn't pay great, but I get a lot of free time that lets me pursue other interests.