The reasoning is more of philosophical nature really. It's a question about what kind of heroes we want the sport and TdF in particular to produce. The riders have often been referred to knights on wheels/iron horses who through so many hardships to create epic tales. In no other sport we get to follow our heroes this close through their ups and downs. We do not experience in other sports that the likely winner of a stage hands the win to someone else for the hard work done.
Winning because the opponent dropped his sword is neither admirable nor epic, it's just a cheap and rather dull kill.
But yes, if Hesjedal is as high as one's expectations of a hero go, then it can be hard to understand this angle.