Supposing you are trying to track a shape-shifting individual... And notice 2-3 different animal tracks, same kind. How exactly would you understand which are the real animal's prints and which those of a shape-shifted Ninja?
Now I know that if you try to track a tamed and named creature in Ultima it will appear with its given name on the list and that would be a valid argument IF we disregarded the fact that someone spent an amount of skill and mana just to confuse their enemies while they are lurking around. I think we can spare them not appearing as animals with player names.
Plus normally you wouldn't even get the names of the creatures, I think this was *allowed* so that it was easier to track your tameables/rideables if you lost them off screen or something.