Are there perhaps political reasons for it? Do investors prefer having two or more founders they can divide if necessary? Does it increase "bus factor" or otherwise derisk the venture?
My opinion: two or more founders who are really invested and work well together > single founder > forced cofounder relationship. I say this as a single founder.
The hardest thing about being a single founder is cognitive load. I don't necessarily mean time. There are usually enough hours, but switching between at least five hats really strains the brain. It can also be hard to maintain energy. I find groups with other founders and working in a good startup oriented coworking space very helpful.
There are absolutely political reasons for it. Both the dividing founders reason you mentioned, plus the fact that single founders are more likely to be technical while when two people found one of them is likely to be a business founder. VCs feel they can control the business founder (or replace him if needed) much easier than the engineer, because VCs are not engineers. (and they are not entrepreneurs in my experience either, though they seem to think they are and are happy to trot out the "exits" they were vaguely involved in, usually via friends and family equity.)
I agree with your priority- a pair of fully dedicated good founders is ideal.
My opinion: two or more founders who are really invested and work well together > single founder > forced cofounder relationship. I say this as a single founder.
The hardest thing about being a single founder is cognitive load. I don't necessarily mean time. There are usually enough hours, but switching between at least five hats really strains the brain. It can also be hard to maintain energy. I find groups with other founders and working in a good startup oriented coworking space very helpful.