Because Locke said so? I don't buy it. He seemed very happy and genuine whenever we won, and dejected when we didn't. Same thing in OKC. Just because someone is cognizant of their stats doesn't mean they don't like winning. Maybe the argument you posted below applies to him as well. He cares because he wants to be efficient.
Barf. EVERY PERSON THAT HAS EVER LIVED LIKES WINNING AND DISLIKES LOSING. That is so universally understood that it doesn't have to be addressed (except for now I guess?). Kanter didn't take the steps to contribute to winning on the floor or in the locker room. Being a winner is so much more than a basic desire to win. Like literally every other thing in life, it's what a person DOES that matters, and what Kanter did was not pass the ball and routinely give up on plays defensively. And because that type of play has consequences, he got fewer minutes and a reduced role, but instead of rising to the challenge of what his coaches told him every day and what people were routinely saying at large, he dogged it more and doubled down on his garbage play.
Let me stress again, liking winning does not make a winner.