Now, before someone "disproves" my point by showing a counter-example, I'll admit this doesn't apply to all founders in all companies, but founders tend to have plenty of money to fall back on. That cushion is what allows them to be founders. If the business fails, well, kinda sucks for them--they potentially lost a chunk of it, but they're not homeless. They'll dream up the next idea and go at it again. Because they can afford to.
Employee #1 on the other hand, is working for a living. They're likely dependent on their employer. They're foregoing a more lucrative salary somewhere else, not to mention savings, 401k's, health insurance. They need to make rent next month. If the business fails, they're scrambling to find another job ASAP. Sure, in terms of "raw number of dollars", they're not risking as much as the founders, but in terms of financial security/stability, future earnings, and career growth, they're taking a huge risk. Shouldn't their reward be commensurate with this risk?