I agree it definitely slows down progress when the team consists of only one or two people trying to fill all the roles. Progress is slowed even more if founder/co-founder are working full-time jobs on top of trying to run the company. My impression was that when taking outside money, investors want the founder/co-founder to be working 100% on the start-up since otherwise progress will be quite slow.
Being self-employed can help because you may be able to take on limited projects to bring in some revenue while still having a fair amount of time to devote to getting the start-up off the ground. Although once a product launches, the start-up is going to require full focus.
One way to get around having limited staffing is to hire sales people on commission once you have launched a product. You also want to identify and enlist evangelists within your target market who love your product/mission so much they will spread the word. (More effective than a sales person).