Humans start multi-tasking (to their detriment) when sitting in front of a computer, because computers are too slow - more precisely, are not responsive enough. Of course, I have only anecdotal evidence for this.
E.g., when I'm reading a book, flipping the page is subjectively immediate. Not so when browsing the web. There is a perceptible lag between pages and that gives time for the attention to stray. (I'm talking about subjective time here, this may not be borne out in real time.)
Mac Mini M4 – Part I
1 hour ago