When a console has other features besides just for playing games, it's no surprise users will use it for other things. Just like a gaming computer, you don't just only play games , you will use it to browse the web, listen to music, etc.
My wife and I use the xbox almost exclusively for netflix, movies, music, etc. It's incredibly rarely used for gaming (sometimes I do Halo nights with some friends)... I do all my gaming on the PC - everything on Xbox just feels old.
If the Xbox didn't have the multimedia stuff that it does, I probably would have sold it a year or two ago.
It would probably get used even more if it could play Blu-Ray movies. I initially purchased my PS3 solely as a Blu-Ray player. At the time it was one of the cheapest Blu-Ray capable devices and being a game console has received continual firmware updates unlike most Blu-Ray players.