You must question the psychology behind collecting itself. Similarly you could ask stamp collectors why they collect stamps that they'll never use on an envelope. Collecting is a strange thing, but don't look into it more than it just being a hobby. Some people hunt birds or other animals as a hobby, but collectors like hunting records (or books) because they think records (like books) are beautiful items. And the hunt itself is fun. You don't need to listen to the records, that's not the point.
Some people collect only song versions, others alternate artwork, others UK 12"s and LPs, others original pressings, others only valuable items and some collectors want every variation out there.
I'm used to having to explain the idea of collecting to non-collectors, but I must admit I'm always surprised as a completist collector to face incomprehension from other collectors who only want song versions or collect for value. I would think that as collectors they would understand other collectors who just happen to look for more items. But no, there are a few people in these forums who I know are collectors and regularly riducule or at least express their incomprehension towards completists. It always surprises me.
Stephane