Its really important cuz because as a Paladin you waste less not tanking anything the only moment you are going to tank its at certain hunts where your AOE damage kill the creatures before being a real threat to your HP and other occasional situations. For example example, a Knight does need to tank cuz because his AOE only damage on close combat but Paladin even at level 150 they can avoid most damage cuz because their AOE hits from distance with Diamond arrows and at Low level still your san can hit from distance. So the answer the only reason is that not taking damage being available to hunt some places dangerous for close combat or low HP at certain levels. Most the time if you can tank the creature being a paladin for more than a couple seconds you are hunting in a bad spot.