Cure Serious Wounds
Why bring up another healing spell? Well, clerics can't cast this until 7th level, and it only heals 2d8+1 damage. So much for clerics being walking infirmaries. The average fighter with a decent CON (+2) will have 56 hit points at 7th level. If a 7th level Cleric with 18 WIS memorizes the maximum number of healing spells, he will be able to cast 5 CLW and 2 CSW. These spells will cure an average of 34 total hit points, hardly enough to keep the fighter going if they get into a major scrap. Strangely enough, druids can cast more healing spells at 6th level than a 7th level cleric. Quite honestly clerics aren't that great for healing parties of adventurers. By extension, this means potions of healing and staves of curing will be extremely useful to high level parties. Coupled with how difficult it is to cast spells during melee, it also means fighters will want to have a couple healing potions on their person at all times.
This spell is fucking incredible, no exaggeration. If the target fails its save, this results in being held for at least 7 rounds (why the description even bothers to list levels 1 and 2 is beyond me), which might as well be death. Further, 3 targets can be affected, or less with a decrease in saving throw. Say an evil priest with a few orc minions meets a party of adventurers. He has a pretty good chance of holding one or two of the fighters, smashing their brains in as the orcs rush the less combat savvy party members. If you're using cavaliers from Unearthed Arcana (on the fence about UA...), paladins are an evil priest's worst nightmare. They already are just using the PHB rules, but all that added crap makes them essentially invulnerable.
To reiterate a point made in my last post, clerics aren't healers. Yes, they can cast heal spells, but quite honestly, paladins and druids are just as effective, which means not really effective at all. Clerics are in fact fighters who can cast a lot of very useful spells that keep a party adventuring. If we look at hit points from a logistical viewpoint, the main strength of a cleric is managing resources. They can create food and water, light, cure poison, detect items and creatures and increase fighting ability, all things that enable a party to stay in the dungeon longer before returning to town. Thus the most important reason to have a cleric in the party is the ability to get more treasure and more experience, leveling up more quickly. If we treat AD&D as a game (wow, imagine that), this is a huge incentive for someone to play a cleric character.