Good paying work is golden handcuffs.
Many of the people who started on the net (90's) were able to do so because they had nothing else significant going on at the time. If they had a high paid corporate job, or even a "normal" paying job, were an attorney, or even ran a small business, they had neither the time nor did it make sense to take chances.
If you have nothing, as Dylan said, you have nothing to lose.
(2) As founders, you should NOT be paying yourselves real salary until you raise significant money. Even then, you should be paying yourselves on the order of $50-60K/year, modulo a few edge cases if you have a family, mortgage, etc.
Point is, founding a startup doesn't actually make sense from a financial perspective. Most often you will be more profitable having been employed.
burn rate = (runway)^(-1)
Reining in your burn rate as much as feasible is one of the easiest ways to extend your runway, and your chance of getting to awesomeness.
A typical job is a better way to maximize one's disposable income reliably next month or next year.