Why Backwards Compatibility is Pointless (But Cool)

Gaming isn't exactly my bread and butter. That'd be movies, obviously, but I'm a fairly avid gamer that always has a least two playthroughs going on at one time, so when Sony announced the PlayStation 4, I figured I take a lot. But, the reveal was less than exciting  you know with Sony seeming to forget that video games are a thing. But, one thing that has stuck with me over the past week has been peoples refusal to get other the fact that the PS4 is not backward compatible with the PS3. And in all honesty, why should it be?