Vectors can already be printed. Vectors types are only dependent on the contained elements, whereas Arrays types depend (until const generics come) both on the

Vectors can already be printed. Vectors types are only dependent on the contained elements, whereas Arrays types depend (until const generics come) both on the size of the array and the contained elements. So whereas a generic implementation of Display for Vec of any length was possible, Arrays required one implementation of Debug per possible length of the array.