There are 'good' reasons, or at least technical ones that make it difficult.

Let's start by talking about PC. PCs run on the x86 architecture and have done so since a little bit after 1981. There have been extensions to the x86 instruction set but they've all preserved backward compatibility. That's why we've never needed a PC2*. You may be familiar with x86-64, sometimes referred to as x64 or amd64. That was when the x86 instruction set was updated from 32-bit to 64-bit. It's all x86 and compatible though.

I should probably explain what an architecture is. An architecture or 'instruction set architecture' is the lowest level of programming language. This is the part that actually tells the CPU how to run (and interact with the RAM, but not the GPU for PCs). Different kinds of CPUs need different instruction sets because the CPUs are different on the inside. The most popular architectures are x86 (for PCs) and ARM (for your smartphones), ARM is optimized for battery life over performance and you'll notice that you can't install smartphone 'apps' on your computer and can't install computer 'apps' on your phoe.

Architectures are named weird because we they're only important to computer people and we let computer people name them.

So let's get on to the Playstations, here are their architectures.

• PS1: MIPS
• PS2: MIPS-III
• PS3: PowerPC. Also used a weird Cell processor.
• PS4: x86
• PS5: x86

Now let's look at backwards compatibility. PS2 was backwards compatible with PS1. PS5 is backwards compatible with PS4. Early PS3 were backwards compatible with PS2, but that's only because those PS3 had a PS2 chip inside of it specifically for this. Nothing is compatible with the PS3. So backwards compatibility is there for Playstations with the same architecture.

Xbox also exists. Xbox1 was x86, as was Xbox2 Xbox3, and now Xbox4. This is why Xbox has an easier time with both backwards compatibility and porting to PC. Edit: Xbox2 was actually PowerPC. I guess this also means the Xbox was just better at porting due to their experience with Windows.

Nintendo also exists.

There are solutions to architecture incompatibility. Option 1 is emulation, as you might be familiar with from PC gaming. You run an entire virtual system on your computer, then on that virtual system you run your game. It's hardware intensive but luckily hardware has vastly improved since then. Option 2 is porting or recompilation, you rewrite large chucks of the lower code of the game to make it work on a different system, this is programmer (and tester) intensive. It's just as hard to port from PS3 to PS5 as it is from PS3 to PC, the only advantages Sony has is their knowledge of the PS3/PS5 and their direct access to source code of the games (or at least some of the games).

There are weirder options, like partial emulation or the PS3 option of just putting an entire fucking PS2 inside the PS3. There's also ways to make doing this stuff easier with interoperability layers (like our dear friend DirectX). There's also remote play, which uses "The Cloud" to run your game on an old console somewhere else and then stream it to you.

*We technically have had PC2 at some point during the PC wars. I don't know what iteration we reached before the IBM PC and it's clones was created. It depends on what you consider to be the first PC.

There are other reasons too! Including pure capitalism and business reasons. However, the architecture thing is a big deal in terms of being a real practical obstacle to backwards comparability. There are other practical obstacles as well.

Conclusion: For the use of corporate closed hardware systems you have been tried and convicted of counterrevolutionary acts. You are hereby sentenced to 10 years hard labor in the code mines. You will be given a chance to better yourself and provide for those that have embraced open(er)-platform gaming.