Several reasons:
- The traditional 9-to-5 goes out the window, people start expecting you to stay late in the weekdays and still be available on the weekends. You can almost hear upper management saying “That's why we pay you so much for”, and unless you own the company there will always be someone higher than you putting that implied pressure.
- You can't explore entrepreneurship outside work and left to fend for yourself after retirement. Usually contracts for big companies prohibit you from basically doing anything while employed, some goes as far as to have intellectual rights to things you do while employed even if you do it outside office hours. So essentially, after you retire you are on your own as you wont earn anything from the decades of work you've done for a company, that's all theirs.
- In certain countries, you are taxed more for a threshold you reach, for example if you exceed X amount of dollars you are charge an additional Y% on the amount you earn. People will say it's because you earn so much, but then again you sacrifice so much time to earn that much. So essentially, you give up most of your free time only to be taxed more. What's the point then? Entrepreneurs find several ways to avoid being taxed. You do the same work and hours as an entrepreneur but not get the same benefit.
- When Sh*t hits the fan, it's all on you, regardless if it was incompetence or insubordination of a colleague.