Science may provide the most useful way to organize empirical, reproducible data, but its power to do so is predicated on its inability to grasp the most central aspects of human life: hope, fear, love, hate, beauty, envy, honor, weakness, striving, suffering, virtue.
Closeness can lead to emotions other than love. It's the ones who have been too intimate with you, lived in too close quarters, seen too much of your pain or envy or, perhaps more than anything, your shame, who, at the crucial moment, can be too easy to cut out, to exile, to expel, to kill off.