I'm not sure about what is really 'simplicity'.. If I program in assembly languages I don't need a huge compiler to generate the executable so the system is sim

I'm not sure about what is really 'simplicity'.. If I program in assembly languages I don't need a huge compiler to generate the executable so the system is simpler but for the programmer it's also more complex because assembly languages are complex and any mistake is really hard to find.. Same for API, the worse is better debate, an OS which retries automatically in case of interrupts is simpler for the users? For most users yes, for those who care about low latency no!