As others have said, I think this is in part a response to more people moving their computers into their home theatres. I have considered getting one for the PS3. Also, I think Apple pushes it as part of their "We are more elegant," aesthetic.

We have one at work in our main conference room which is very handy, though, allowing anyone sitting at the rather large conference table to control the PC sitting under the table hooked to the projector. It doesn't require separate batteries; when not in use it sits in a little charging dock.

I was very annoyed when I discovered that the only trackball I could get to fit my usage profile was wireless. That has been an utterly pointless waste of batteries. It never moves! I would also request a wired keyboard for my regular computer for that reason.