There has never been a 1:1 relationship between how essential a job is, nor how difficult it is, and the pay. It's mostly about a) the barriers to entry, which can be academic (law, medicine), regulatory (law, medicine, probably finance?), institutional (finance, tier 1 law), or just how grueling it is to get through (definitely medicine outside of some specialties like family med or peds, probably tier 1 finance/IB too); b) leverage/BATNA. A is more systemic - it drives wages up or down as an industry and is why a family med doctor makes $200k/yr but a radiologist makes $600k/yr. B is more localized, if I have a lot of leverage or my BATNA is "sit on a beach and drink" I might pull a $400k TC instead of $300k simply by waiting around for a better offer. The more people in my field have that opportunity, the more of a systemic pressure this has on wages.
Anyone can be a teacher. The certification requirements are low. The academic requirements aren't anything more than most kids are getting anyway (a degree in anything will qualify you in most US states). Most teachers need to work so their BATNA is "work someplace else doing the exact same thing for roughly the exact same amount of money." What's more (and I didn't really mention it above) is that you can't tie teaching directly to income. Not that you should be able to, but if you're a quant at an HFT shop you can probably draw a line with a pen from your code to tens of millions of dollars in profit that's there this year that wasn't there last year. Do that year over year and it's hard to argue against you getting paid $800k-1M/yr in cash and bonuses. Helping one of your students read a little better, or finally understand linear algebra, isn't going to increase your personal bottom line at all.