That and people who fail/drop out of harder pursuits such as the BAR exam usually teach this subject (or history) as they have (most) all the credits necessary to transfer majors.
I had a teacher like this; felt so bad for the dude.
Tried to become a lawyer cause his mom pushed him to be like his older brother. Went to one of the top schools in the US; but he quickly found out he didn't have the chops or the will to keep pursuing this major and dropped out. He said his choices of jobs using his current credits and not going back to school; essentially amounted to history/sociology teacher... so that's what he became.
To add insult to injury (at least at the time I had him as a teacher); he was classified as a substitute and got paid 13k a year for a school who has a teacher on tenure who was milking maternity leave for well over a year and a half according to him.
Dude was getting fucked royally and at the expense of the kids too. Man didn't get paid enough so he litterally had 2 additional jobs after school (he was a soccer and MMA coach surprisingly); so he almost never came in with a prepared lesson plan.
I remember just about everyday him googling a lesson plan related to what we were learning and we'd just go along with some video or assignment someone else made. Shit even grading was a joke; he'd have us make our own rubrics and then have us grade ourselves lmao.
God bless that man tho, he was a good dude who was trying his best. Hopefully he's getting paid what he deserves now; but yeah this is how you end up with teachers sometimes 😅🤷‍♂️