why is array size limited when declared at compile time?

Question

for example I can do

int *arr;
arr = (int *)malloc(sizeof(int) * 1048575);

but I cannot do this without the program crashing:

int arr[1048575];

why is this so?

Answer 1

Assuming arr is a local variable, declaring it as an array uses memory from the (relatively limited) stack, while malloc() uses memory from the (comparatively limitless) heap.