There is a history to it; in one of the predecessor languages, like B, Ritchie actually had arrays that had a hidden pointer to their start. The "array to pointer decay" was actually a real operation that loaded an address from memory, and it was possible to twiddle the bits to relocate an array. One problem with it was no way to initialize such a pointer field that would allow an array to live in dynamically allocated storage (no constructors in the language).

So in short, the bad design (array values produce pointers) was informed by conceptual compability with an earlier design in which that was literally happening.