I am a high performer (because my boss is a dick...I'm my boss) and I work everyday with a twitch stream of Hearthstone running on my laptop. It's background noise that helps me focus. When I need a little break, I tune in and pay attention.

Try not to project your own limitations on to other people!

There are enough studies which tells you that we are not good in multitasking. It costs you more resources.

Depends on what I'm doing. If I'm grinding through stuff I know exactly how to do, but can't automate away, I find having something like people talking or an audiobook I know well running in the background actually helps me focus. It occupies just enough of my mind that I don't feel tempted to get distracted by the internet.

I have a whole range of preferred noise depending on the task, from dead silence for hard, tricky problems up to what I just described for easy but important detail work. I even know exactly what kind of music I want to listen to for different tasks, and whether or not I want vocals in it.

There is no one-size-fits-all solution to what works for people.

I do the same thing. I can listen to talk radio and read a book at the same time. I get similar responses to what you have said here.

There's probably some relation between this and growing up with the TV on 100% of waking hours, even when no-one's watching (which is really common).