I often see a disconnect between perceptions of expected success of founders and engineers. I've observed this is particularly pointed for non-technical founders. To generalize, a young entrepreneur with some success under his belt is starting a company. As far as he's concerned his company is all but guaranteed to succeed: he's got the experience and sophistication necessary to make this happen, the team he's hired to his point is top-notch, he's got the attention of some investors, the product is well thought out, etc. He approaches an exceptional engineer and extends an impassioned invitation and... the engineer balks.
What happened? Is he delusional about the company's prospects, thinking he's got a sure fire hit when he's actually in for a nasty surprise once his hubris collides with reality? Is the engineer a square who would rather work a boring job at a big company than live his life, and wouldn't be a good fit for the team anyway?
I propose a different resolution: our confident businessman is certain about the success of the company, not the success of the engineer as part of the company. He knows the company's success is going to rocket him into an elite circle of Startup Entrepreneurs. The engineer, on the other hand, doesn't see the correlation between the company's success and his own: even if the company takes off to the tune of eight to nine digits, his little dribble of equity is just barely breaking even over the comfortable stable position he's in now.