What definitely-not-selfless reason do you have in mind? It seems to me that Kel does care - when Yeden got the rebels slaughtered, Kel wanted to attack the army to save them. It was only Vin who held him back. Also, he had Mare's flower. He wanted to make the world the way she had imagined it. Yes, he was a bit selfish, but I think his ultimate motivation was selfless.