I just quit my job to start a business with a friend and I thought the reaction I received from my coworkers was interesting. Most were genuinely confused, didn't understand why I would want to quit, and were surprised that I would do so without any guarantee of employment somewhere else (somewhere that isn't a non-funded startup).
One manager, at a loss for words, just asked (in a weirdly childlike way) "why?" And I didn't have a good answer for him. Because I can't imagine staying at this job until I'm middle management? Because I hate the internal corporate pressure to produce crappy software? Because I want to set my own schedule and have a shot at wealth that will give me freedom from the 9-5 before I'm in my 60's?
I want to be free, and I want my son to be free.
I think many people have a deep aversion to being unemployed, or are scared of being in an untenable financial situation. If I have an unexpected expense in the next three months, I'm screwed, and that's a scary place to be in. It's not a place that most of my coworkers have ever been in. It's been a while since I've been in that place, but I have been there, and rolling the dice with your home or vehicle on the line is easier when you have had the experience of doing so, failing, and recovering from that failure. If you were raised middle class or in stable poverty of some sort, you may never have found yourself with all of your belongings in a rucksack and then come back from it.