Because most of the peerages automatically extinguish in certain situations (e.g. no male heir, no heir at all, or sometimes if their holder is King / Queen), t

Because most of the peerages automatically extinguish in certain situations (e.g. no male heir, no heir at all, or sometimes if their holder is King / Queen), they will gradually die out over a long period. This is also a sign that they're not a modern (or even modernised) institution.