I think you are confusing founders with leaders. Companies do not need multiple leaders. Just like teams, however, they do need multiple players, each providing different skills.
PG thinks that you have to have consensus and multiple founders all with an equal say. Thus, multiple leaders.
The whole cofounder thing has taken on quite a weird perspective-- I think because PG doesn't have much experience with it, but is adamant, and most of his readers have never worked for a startup, let alone started one, so they believe he's preaching the gospel.
There has to be a leader, that's my point.