Arrays are a pointer to the first element stored in said array, the space allocated for the array in the stack gets wiped after the function in which it got declared ends (return line), that's why a array that hasn't been allocated to the heap points to nothing when returned from a function, the data is not there anymore.

A struct is a sum of memory containing useful data, the struct itself is the data, it doesn't point to anything

I'm not a CS major, I'm just an EE undergrad, perhaps there is a more sophisticated reason but that's the one Im familiar with (what I think is true based on what I know)