It is useful when the "normal" flow is to terminate the loop early with a break. For instance, in a linear search algorithm:

    for x in li:
      if x == to_find:
        print("found")
        break
    else:
      print("not found")

Logically, the "else" matches with the "if" introducing the "break" and means "if none of elements cause the break branch to be taken".