They are. It is simply their nature. It does not seem to be as common in the general population, so one can assume the seal merely selects many with similar traits.
I fight it because I wish to. Because the alternative will cause more pain and struggle than the fight against it. For me, and for those I care for. It its more than mere companionship. It is not something that can simply be acquired at will. Without it, I am not certain I would care to fight.