Living with someone and being married to them requires an intimate understanding of who they are as a person. Being able to work through those hard times is something I can do. Being able to make the hard decisions is something I can do.
Being able to go without a salary for 4 years, own a house, provide for a family, and work on a startup is something I couldn't do. In fact no one talks about this. I suspect many founders are either:
a. working on their second startup and have a huge bank account full of cash from a pervious exit
b. come from an extremely wealthy family where money has no effect on their decisions
c. are in fact paying themselves a salary (and hiding it from investors?)
d. have a significant other that can support the entire family