Axolotls shouldn't despawn and respawn

I don't get why axolotls despawn over time if not caught and released from a bucket. They're animals, and most animals ( as far as I know only exceptions are ocelots, cats and ambient mobs?? ) do not despawn. The game shouldn't despawn and respawn axolotls over and over again ( which is what I expect to see in future snapshots when they spawn naturally ).

Due to axolotls being endangered, I would make it so they don't despawn, but also don't respawn once killed, making them vulnerable. It also makes the player think "I shouldn't kill these, they won't respawn!", which is what they achieved with pandas too, which are also endangered.