@Shahrazat I think most players don't really care to kill the kill leader, because most people just want to get as many kills as they can get in the game. Therefore, someone else's kill count may be irrelevant to them, when most players' focus is on a winning game with a lot of kills.
That's just my opinion. Also, as previously mentioned, a separate mode with this feature might actually be a cool idea!
People would play it purposely to have people "chase" them. Why you might ask? Maybe a squad wants a high kill game, and they want to fight the whole game. However, playing the devil's advocate, people might play it and just run away from the kill leader. But I doubt the later would be more likely.