Apart from the usual Gates/Allen, Jobs/Woz, Larry/Sergey anecdotes, there's little evidence that two is a natural lower bound on the number of founders. It's sometimes claimed that a startup is "too much work" for one person, but the productivity of individual programmers is not fixed; with today's tools, solo founders can be as productive as a dozen developers from fifteen years ago. Another common argument is that you need a cofounder as a sounding board and as a source of moral support. These roles are vital, but they don't necessarily have to be filled by a cofounder. Einstein needed the help of his friend Michele Besso to develop special relativity, but Besso wasn't a coauthor on Zur Elektrodynamik bewegter Körper.
Unfortunately, the need for cofounders is a deeply entrenched belief among investors, so much so that it risks becoming a self-fulfilling prophecy.
A big issue for investors is also the survivability of the business. Investing in one founder is a risk. They can get sick or take a long leave due to a family crisis. Investing in a team greatly increases your chances that the business is going to continue to exist.
It's something that investors most definitely think about. Investing in early stage companies is often a decade long investment. A lot can happen in that decade, and minimizing your risk is important.
It seems your problem is its own solution; I would argue that many of the productivity enhancements you cite as allowing one founder to go it alone also enable founders to go without investors.
This is definitely true to a certain degree, which was one of the points of the linked article. But it's still lamentable that some solo-founder startups that could benefit from funding will fail to raise money because of irrational investor bias.
well yes. I mean, my company would probably also benefit from investment; it is a rather capital intensive industry, after all. In my case, though, I think there is at least as much irrational bias on my end as on the investor end.
Unfortunately, the need for cofounders is a deeply entrenched belief among investors, so much so that it risks becoming a self-fulfilling prophecy.