The only reason that ended is to resell you the same games again and again. I have several game systems in my living room, if I buy a PS4 the PS3 will have to go or the cube, or the n64 or the PS2, I have no room left.
I would have bought a PS4 at launch if it included backwards compatibility and sold my PS3. Now I will not likely be buying one.
Yes, that's the only reason. It's not that the Cell processor was a non-starter and extremely difficult to code for, it's not that Sony is trying to reduce the cost of hardware manufacture and software development, and it's sure as hell not to make ports of PC or Xbox-centric games easier. It's so they can resell games. Yes, they can emulate the PS3. I'm sure emulating a 9-core processor on an 8-core processor will work perfectly at full speed with no sync issues! Or they can include the PS3 hardware and jack the price up by another $250. That will go over well with consumers! You have the option of buying a backwards-compatable PS4. I simply refer to it as "A PS4, PS3, and a roll of duct tape." Toe-MAY-toe, toe-MAH-toe, right?
It's a little like being slightly drunk at times. You go to press a key and somehow miss and hit the one next to it, or your muscle memory doesn't seem to work.
Hell, I'm young without medical problems and I get the same thing. It's not just for old people any more!
To understand a program you must become both the machine and the program.