Why Are the New Systems Not Backwards-Compatible?

So, the Playstation 4 and the Xbox One are now available for purchase, which is great, but I have heard that they are not backwards-compatible with their earlier incarnations, which I find to be both odd and displeasing.

Why would the manufacturers of the new systems not make them backwards-compatible? Do they simply expect the players to give up their older systems when they purchase the new systems? What if a player wishes to continue playing their old games after purchasing a new system? Will they need to keep the older system to play the older games? Surely, it cannot be that difficult or expensive to make a system backwards compatible, and doing so would also be a way to ensure that one's customers remain with you? If I were a manufacturer of a video game console, I would definitely wish to retain customers, and having my consoles be backwards compatible would be an excellent way to ensure that, in my mind.

What does everyone else say? Why are the newest systems not backwards-compatible with their earlier incarnations? Why do you believe that the companies made this decision?

The biggest reason for why the PS4 isn't compatible with PS3 is because of the cell architecture of the PS3 chip, which was abandoned with the PS4.

The reason why old games don't usually work on new consoles is the fact that console games are programmed differently than PC games. PC games have to work on 1000s of different hardware setups, while console games are programmed for one hardware setup, which means that the games can be very specific to the limits of the console hardware. So when a new console is made, the hardware is different which means that the specific programming will usually not work.

I remember early PC games literally ran as fast as the CPU would let them. When my family got a new computer, all of a sudden pac-man and tetris ran way, way too fast and became unplayable. Imagine similar issues.

The Xbox One is similar to the situation with the PS4 that d_stilgar mentioned. For both consoles, moving to 8GBs of RAM meant that they needed to restructure the OS and doing so meant that the previous gen games would need to be emulated to run. An emulation environment takes a lot of system resources (check out the requirements for good performance on Dolphin to see what I'm talking about, that was a much older console than the PS3/Xbox360) so emulating either last gen would have likely resulted in performance that was WORSE than just keeping your old consoles. That would have led to people saying that the new consoles are "slow" or require additional hardware that would have increased costs further.

Personally, I'll hold on to both my 360 and PS3 and hopefully add an Xbox One into the mix down the road. There are enough new features to either console that I think they will be interesting but not enough that I'm jumping in until at least Halo 5 is out.

Dunno if this really counts for anything, But you can play the old xbox through the new xbox via the HDMI port.

Though i dont really see the point of having two systems running just to play one game.