Why do fighters say that? It's a fight the point in a fight is to render a fighter helpless either by making them tap or knocking them out... If it goes to a decision did either fighter really do enough to win? Should they be allowed to complain? 
Considering a decision is one of the potential outcomes of a fight whether you try and finish or not, it's still relevant to want to have been the guy who did more to win if it reaches that outcome. Frankie evidently felt he did that, whether you believe he did or not (and I don't).
Or, you know, you can NOT concern yourself with the potential the fight might go to a decision, lose, and get paid a lot less.