And why should they know? They don’t think they should. I think differently — I think (and it might just be me) that in order to fully understand something and how that something works, you should learn about its origins/roots. Of course they never once thought to ask why their iPhone keyboards are QWERTY. But if they did…it wold lead way back, back past the typewriter in this picture.
Same goes for SEO — you can’t expect to master something (task/tactic) without knowing why it works and why the things around it work the way they do. Trust me, I know people who do SEO but have never heard of micro-data, but that’s another story.