Because game development is what's called "successful product industry" which means sometimes you have to make 10 failed games to finally release 1 successful. Majority of game studios don't make it and competition is very high which means game budgets is race to the bottom.

Also platforms like consoles and Steam take their 30% cut, then publisher / investor take their 30-60% cut and you also have to pay taxes on every step. Usual game studio that working using publisher or investor money only get 20-30% of gross sales.

Large companies are able to make conditions better and they actually have higher salaries and better work life balance whithin the market, but since for everyone else it's run to the bottom they have countless number of potential new employees.

PS: I am CTO of small game development company and to make games I have to be okay that I'll earn 3x less than I would as middle software engineer in fintech. Game dev is tough industry to work in, but it's always by choice.

Literally everyone who works in game dev are able to find better paid job elsewhere: gambling, marketing, fintech, etc. People just love making games and dont want to move elsewhere.