Why is it so hard to leave a corporate job if you hate it so much?

I have run into many people inside corporations who express intense loathing for the organization that provides their paychecks.  They say things like:

"This company is run by a bunch of egomaniacal, power-hungry and greedy jerks who only care about making a profit."

"I don’t trust my manager farther than I can throw him.  I know that he is conspiring to outsource my job, after stealing my ideas and sucking every last drop of creative energy I have."

"I feel like I want to scream when sitting inside boring as hell meetings all day.  They serve no other purpose than to annoy all participants and keep us from actually doing productive work."

Jeez, if it is so terrible, why don’t they just quit?

1. There is an illusion of security when you work for a corporation. I use the word illusion very specifically since it is totally unsupported by recent fact.  Outsoursing, mergers, reorganizations and market instability all support the fact that your job is not very secure in a corporate setting .  But, like being in an abusive relationship, we think "if I just work a little harder, maybe he will change."
2. It is easier to tell your father that you work for IBM rather than are taking a year off to write a screenplay. We do love our parents, and most are firm believers in the myth above, since in their generation, large corporations did provide a much better chance at stability.  Not to mention that they think a lot of your desire to "find meaning in life" and "contribute to a larger cause" is probably just another example of the liberal media destroying fine young minds.
3. You can’t beat the benefits. It is hard to argue this point, since you can get exceptional benefits when you work for a corporation, including health, dental, retirement, life insurance, medical savings plans and vacation and sick pay.  If you have a family, this can be a huge issue.  But I will say from personal experience that it is not impossible to create a similiar package of benefits while self-employed that give you the same sense of security.
4. It is too scary to step into the unknown world of self employment.  Even though you might loathe your current job inside a corporation, at least you know the rules of the game.  You don’t have to think too hard, or work too hard, to bring home a decent paycheck.  If you want to step out on your own, all of a sudden you have to know about all kinds of things like accounting, legal matters, sales and marketing, product development and distribution.  The prospect can be overwhelming and it is easier to just stay where you are. (if you want to see what you DO know about starting a business, you can go to Free Stuff at ganas.com and take the "Test Your Small Business Start-Up IQ" assessment.)
5. You really want to leave, but you just don’t have enough money saved to make it through the cycle of a start-up business. It does take money to undertake a new venture, even if you are just going to go from being an employee to an independent contractor.  Start-up costs vary wildly, depending on the tact you take and the nature of the business you want to get into.  This particular problem can be overcome by getting extremely clear about the capital you require and making a concrete plan for raising the money.  You can choose to stay in your corporate job for awhile, with the specific purpose of being your own venture capitalist and generating money to fund your new venture.

Those are my reasons, what do you think?