You can't compare being a teacher with a career in "law, medicine, politics, or finance" or a programmer. The latter all require very high intellectual aptitude, either logical/mathematical (programming, finance), memory (medicine, law) or social intelligence (finance, politics). In contrast, mostly everybody can be a teacher (and according to comment [1], teachers usually come from the bottom of their class).
[1] https://news.ycombinator.com/item?id=9090437