Because you're using Unity or some other cross-platform engine, right? There is practically no similarity between a PS3's Cell, PS4/Xbox One/PC/Mac's x86 and the IPhone/Android ARM architectures - some are von Neumann, some Harvard, some a bit of both. The instruction sets are different, they use different RAMs, different internal structures... And that's just the hardware differences. That you can compile a high level language into assembly or machine code that any of the platforms you mentioned can run is purely a result of Unity (or whatever other multiplatform engine you're using) supporting those platforms as an interpreter and the fact that it doesn't rely on proprietary APIs like DirectX (because if it did there's no way you'd be able to run it natively on Mac OS, for instance). If you wrote your program for PC in a low level language there's no chance it would run on a PS3.
I mean, any IDE where you code in, say, C, Python, Perl or other high-level languages (i.e. programming languages that are human-friendly but nonsense when entered directly as machine code) has to translate what you've written into something the machine can understand, which at the lowest possible level is literally a long string of binary. That means if you write a program in C then compile or interpret it for x86 and Power (which is what the PS3 uses), the machine code you get out will be different and not cross-compatible.
That said, congratulations on making your own game, how long did it take and how hard has it been? Did you have any prior software experience? What was your process? I'm interested in developing my own game because I've had an idea in mind for a few years now and I think I want to try and make something for myself.
