A couple reasons: with the probable decline in numbers of students (particularly international students) I see furloughs and firings in the future at my former university. Pay cuts and furloughs are coming in my industry as well, but because the base pay is higher, there is farther to fall -- and I mean that in a good way, because I'm still living as if I made half my salary.

But more than that, the part I actually liked about teaching was that person-to-person engagement. The arguments, the exploring, the discovery. Seeing people (students) rise to challenges and do things they didn't think they could do. I've done a lot of online teaching, and certainly some of that can happen, but especially with struggling students -- they just don't log on. They slip away. At least if someone's sitting in your classroom you can provoke them or cajole them or charm them into a reaction that you can tease into engagement.