I think part of it is that running a startup going for investor money requires similar social skills to running a startup with a co-founder. These skills are n

I think part of it is that running a startup going for investor money requires similar social skills to running a startup with a co-founder. These skills are not required, and sometimes don't exist in the lone founder. The big difference, I think, is that if you have all the equity, really all that matters is your will and ability to go on. Sure, your employees, friends, spouse, etc... are incredibly important, but dealing with a friend, spouse or employee is a rather different thing from dealing with a cofounder