The people who define Cs abstract machine are well aware of what real hardware is like. The standard of course doesn't mention real hardware but what is in there is guided by real hardware behaviour. they add to the specs when a change would aid real implementation
The ommitte empers have been awareof simd for a long time and asking that. So far they have either not agreed, or because they have seen no need because autovectorization has shown much promise without. (that is both of the above are true though not always to the same people)
multi core is where languages have had to change because the language model of 1970 wasn't good enough.
How should they? in some cases they have decided that isn't where they want c to go, in others the model of 1970 is still good enough, and in others they are being slow (possible intentional to not make a mistake)
