Why do some people assume that everyone hates their job

I'm seeing more and more comments on WSO defending IB's work culture by saying that all jobs suck. Now I don't disagree that few people actually love their profession, but isn't it a big stretch to say that most people despise their line of work. I have plenty of friends and classmates who work in tech, business development, etc. and they rarely moan about their jobs. They make pretty decent money and have a life outside of work. What is it about IB that makes employees so miserable, but at the same time defend it so intensely by putting down other jobs?