It all made sense.
Paladins were not AoE healers. They were single-target healers. More specifically they make a /cast [target=nameoftank] Flash of Light macro and then poke that button for a few hours. It was amazingly boring. It was amazingly bad at anything else. It was amazing like a terrible movie that you somehow can't stop watching.
Then Blizzard ruined it all.
Paladins are sort of AoE healers. But they are still single-target healers. I blame Beacon of Light. It made everything backwards. Now the best way to heal is to heal everyone except the tank.
What's next, they turn into a melee spec and heal through melee attacks? Will they punch people to life? If you're confused on the concept, watch episode 15 of Red vs. Blue for a demonstration of the proper technique and effectiveness.