Brooks law “Adding manpower to a late software project makes it later” is just the surface of some of the metaphorical language that has most stuck with me: large systems and teams quickening entanglement in tar pits through their struggle against coordination scaling pains, conceptual integrity in design akin to preserving architectural unity of Reims cathedral, roles and limitations attempting to expand surgical teams, etc.
Love a good metaphor, even when its foundation is overextended or out of date. Highly recommend.
Mostly it's because when we hit a point where one person would get stuck, the other usually knows what to do, and we sail through almost anything with little friction.
And to your point, a single person can easily get stuck, I know that applies to me many times.
I don't get why people try to simplify - you're removing important details that determine performance and therefore output. This leads to false conclusions.