This is a nice feature. Most cable and satellite providers have this.
Better example is I'm watching a car building show. My wife hates watching those shows. So we switch to a show we both like. She gets up to do something else and I just hit the "back" button. This button is on our DirectTv. This back button goes right back to where I quit watching in my car building show.
Also there is an option with most cable/sat providers to do PIP. This is handy for my wife because she is a football nut and likes to flip back and forth between games and watch several at the same time.
As a software developer this really wouldn't be that hard to implement doing a back button to the last location you were at in the system. It would take very little memory and be a very handy thing for a lot of people.