IME, children (I have 4 of them) have extremely high concentration levels, if they choose the thing they're concentrating on. My 8yo will read for hours, uninterrupted. My 6yo reads for 30min+. Even my 3yo will happily look through picture books for 15-30min.
Well, if you happen to be a music teacher for kids you see the very poor concentration levels of the average kid.
You also see the progress of it over time and age.
And that nearly every parent is overestimating the skills of their own kids.
Children do have the same behavior, before they learn to sit down and concentrate.
We are becoming children again. Everything should be super easy. This is what sells. A tablet for example has the haptics of a babies device.