Jokes on FT, we have both
In my case, I did consider becoming a teacher for IT stuff. Not really "IT", as pupils would first learn the basics of course, and the really interesting stuff might not even fit into the curriculum, but I could well imagine teaching what I know and maybe even establishing an extracurricular computer programming club or something. I would feel great passing on my knowledge. But what second subject to teach? ... The only other applicable thing I had in some amount during my studies is ... math. Ugh. You telling me I might have to take additional math lectures, with people who study to become math teachers?! No friggin way man. Also am not a native English speaker, and while I use English every day all day long, I don't think I have the detailed knowledge to teach it responsibly to students, unless they are total beginners, but I won't be teaching IT stuff in primary school, now will I.
If you stick to only one subject, perhaps they will tolerate you, but your salary will forever be a reduced one, even if you work the same hours, just because you only do one subject, and no matter how much of an expert you are.
When it comes to IT/software engineering I don't think there ever was a shortage. Just businesses, implementing big tech hiring processes for their tiny startups and then playing surprised pikachu, that they are "not finding talent".
Aren't those hurdles put in by teachers' unions to ensure they maintain a leverage over their jobs market? Same is for doctors, notaries, etc in a lot of countries.
The intention is to destroy public education in favor of private schools. Same as public health care has been systematically destroyed. It's all part of the neoliberal agenda.
Or take mental health care. We have enough therapists but we don't allow them to work with patients on public health care. We give that license only to a select few ensuring that people wait 6 months to a year if they want to get a therapy spot. Otherwise too many people would get therapy and that would cost money.
The goal is to make rich people richer and ensure they have enough desperate and cheap labor to exploit.