Well, first, that hypothetical situation never happens. Of the top 10 guys with QS, the highest ERA is 3.42. The next 10, only one is over 3.50. The next 10, only two over 4.00 (barely). Second, it discounts that one of a starting pitcher's jobs is to not burn the bullpen. Third, when these two phypothetical pitchers left, both pitchers gave their team a decent chance to win, but one was able to save the manager from having to have 30 extra innings tacked onto an already overworked bullpen.