Of course I wouldn't do it for 20k, there are much easier ways to earn 20k. Real world - I work in an industry that is young. You either move up, or you lose your job. I'm one of very few people my age still working in this industry - it's tech driven, so the younger you are, the more you have value for "craft skills". So if you want to keep earning as you get older, you have to acquire management skills.
As to why I do it, family redundancy whilst on ML forced my hand. Up until then, I was a bit less ambitious. And then I realised that in order to feed my family, we were not in a position for me not to work, or to work in a half hearted way.
And I never suggested on this thread that my job was more valuable to society than others - it's just more valuable to the shareholders of the company than others. They pay my salary.
I also spent the afternoon (not in the UK right now) working on a project that will help millions of the worlds poorest people access the internet. As part of my package, I negotiated a minimum period of time for me to spend on pro bono work that gives back to society in some way.
And I'm a bloody good mother - my DD is happy, secure, and confident in my love. I had her late in life, and my earnings level means I should be able to retire early - so will have lots of time to spend with her. She travels with me a lot as well - so has seen so much of the world.
It's not everyone's choice, hence why companies will pay lots of money to people who are willing to do this and have the skills to deliver. Doesn't make it a wrong choice, though, just one that's different from yours.