In my case it was initially just being extremely dissatisfied with my life and deciding to do a startup. Which is kind of like realizing your car is out of gas

In my case it was initially just being extremely dissatisfied with my life and deciding to do a startup. Which is kind of like realizing your car is out of gas and deciding to push it across the desert for fun. Eventually I found something which grew into pure unwavering passion. Unfortunately that doesn't automatically translate into being able to execute successfully. The other reason was a desire for massive amounts of wealth. Not for the sake of it, but because I'd love to be able to spin up large projects left and right. Paraphrasing another comment: the deep desire to do things better. And of course, make the world a better place.™ Funny enough, I spent about an hour writing a fairly heartfelt ten paragraph reply to this question, until Firefox mobile crashed and lost it all. Then I realized that reply was an explanation of what keeps me going, not what motivated the decision to start in the first place. What keeps founders going might be a far more interesting question, and certainly a more complex one. It's a psychological minefield: career and personal life opportunity cost, sunk cost fallacy, people depending on you. Much more messy than the simple why of starting.