Apple actually had something like this in the mid-90s called "At Ease", designed as a child-safe file manager. You had programs on one tab and files on the other. I remember it from elementary school, and always felt that a more modern version of that would help less computer literate people.
More precisely, they want a backplane into which they can effortlessly plug in various appliances. Press Buy, download it, plug it in, it just works.
Open Mail, type letter, hit send, hear "sent mail" swoosh.
Open Safari, enter URL or search term, click Go, get webpage.
Push lever, insert bread, wait 30 seconds, eat delicious toast.
Open Word, type stuff, hit save/print/email, get happy boss.
Open Youtube, enter search/URL, push Go, Laugh.