OK, maybe it doesn't but it's definitely overrated. And I can't do it.
I sometimes have focus so intense that someone walking up behind me and saying "hi!" can scare the crap out of me. Like heart-leaping scared. So flipping my focus back and forth between two things is just a huge drain. And it's totally not worth it.
So it's good to hear other people in support of a ban on unnecessary multitalking. Singletasking is where it's at. All the cool kids are doing it.