One advantage could be ease of refactoring. Imagine starting with "goal: the list is sorted", but the resulting program is uses too much space to achieve it. It

One advantage could be ease of refactoring. Imagine starting with "goal: the list is sorted", but the resulting program is uses too much space to achieve it. It could be a lot easier to add "goal: the list is sorted in O(n) space" than it is to rewrite your sorting algorithm.