We speakers of English are a possessive lot. The trait is built into our language, all that apostropheess stuff like "my brother's keeper," "the horse's mouth," and "someone else's opinion." We like to know what belongs to whom.
Possessives endow us with a comfortable sense of property, of owning, and--even more important--of belonging. They suggest that nothing in this world is unattached, that none of us is an island.
Ours is nearly the only language that uses that peculiar apostrophe-ess way of showing ownership and belonging: "my brother's keeper," "the horse's mouth," "someone else's opinion." Most other languages say something like "the keeper of my brother," …