Because Unity's home is likely to be mobile and web. It's more centered on mobile and web than it is, say, on game consoles, and mobile and web are more suited to things that aren't necessarily games, right?
If you have a character that's like happening on a game console, he's going to stay the game console guy. But if you've got a character doing cool stuff, you know, in your games on your PC or on your phone, it's not hard for him to start then giving you the weather or the times at the movies or whatever.
Further, since people are doing non-game things on their mobile and on their web, there will be opportunities to use Unity for non-games there because to have meaningful 3D characters, you need an ubiquitous 3D solution, and it will be there. And then further, it's got multiplatform, so if you want these characters to follow you throughout the day...
This interview with Jesse Schell (the guy with the DICE talk about gamification) is interesting for its bits about Unity and, well, everything else too.
Given how much my family all loves Talking Tom Cat for Android, I can see portable multi-app characters taking off.