If anything, I'd blame compilers here -- IMO, they should automatically throw at least a warning any time they need to pad/rearrange a struct to make it explicitly clear to developers what's happening.
Even the old language spec from 1989 talks about an "abstract machine with the expressions being evaluated as specified by the semantics". One of the first chapters 1.2 Scope makes this very clear and then 2.1.2.3 Program execution clarifies this even further. Other things to note is that the spec doesn't mention variables being ever stored on the stack, instead it's called automatic storage, see "Storage durations of objects", the word stack is not even mentioned once throughout the whole spec.
Today with modern CPUs all this is even more important, if you think you are operating on a global memory array you are doing it wrong.