12tone: What's the point of a prechorus?

A great video by the music theorist 12tone, about the - prechorus, a relatively recent invention in Western popular music, which quickly established itself as an essential part of a song. "A good prechorus not only elevates the chorus, it transforms the song, changing its narrative and musical structure to more effectively tell certain kinds of musical stories. But where did they come from, and more importantly, how do they work?".