Here's the thing: people who aren't geeks often like and even prefer single-purpose devices. There is, as has been noted (see http://g4tv.com/videos/44277/DICE-2010-Design-Outside-the-Bo... ), a "pocket exception", but for larger devices, people who aren't us are often intimidated or confused by devices that do many things. And of course there are dangers in making a machine more general-purpose than it needs to be.…
Let's start with the iPod. Everyone uses it to listen to stuff. My brother listens to rap music, almost exclusively. My niece listens to whatever boy band is en vogue today. Very different genres of music. I love audiobooks on mine. Along with music. I have an aunt that has church sermons on hers.
Move to computers. I have not used a word processor in months. I spend a helluva lot of time in spreadsheets though. My niece, with her school reports, is the opposite. My nephew is almost exlusively a gamer on his computer.
Even the web. Most people have a dozen or so sites that account for 90% (made up stat) of their browsing time. It is a different dozen for all users though.
So yes, the vast majority of users will use their devices for only a handful of purposes. It will be a different handful for each user though.