Jack Daniel
dice-universe.blogspot.com
Clerics are the original gish.
Chainmail, the miniatures game that was a precursor to D&D, has wizards but no clerics. They have 14 spells, most recognizable as modern-day wizard spells, in 6 levels of complexity (which seems to be a modifier to the spell rather than a property of a spell itself). There are no clerics.
Going back to the earliest D&D rules, the D&D white box, we actually have cleric spells up to 5 and magic-user spells up to 6. The table even has a line showing the lack of cleric spells at level 6, indicating Gygax and Co. at least noticed this. Interestingly, clerics get 5th level spells at level 7, whereas magic-users (as they were called in 1st edition and earlier) have to wait until level 9, finally getting 6th level spells at level 12. Clerics also have no more than 6 spells per level, whereas magic-users have as many as 14 sometimes.
From the original description of Clerics: "Clerics gain some of the advantages from both of the other two classes (Fighting-Men and Magic-Users) in that they have the use of magic armor and all non-edged magic weapons (no arrows!), plus they have numbers of their own spells. In addition, they are able to use more of the magical items than are the Fighting-Men." They're an archetype now, but they were the original gish class!
So, the short answer is: they're not supposed to be as good magic-users as magic-users.
They can heal, though, which Magic-Users can't, which wound up making them the third point of the archetype. Interesting how these things develop.This is what I would have said.
To reiterate what you said, in the Original you had Fighting-Men and Magic-Users. The class that incorporated both were Clerics. They weren't supposed to be as good of fighters as Fighting-men, and were not supposed to be as good of Spellcasters as Magic-Users. They were the middle of the two different types of characters.
I also remember reading they were invented to fight a player's vampire character called Sir Fang.
Chainmail, the miniatures game that was a precursor to D&D, has wizards but no clerics. They have 14 spells, most recognizable as modern-day wizard spells, in 6 levels of complexity (which seems to be a modifier to the spell rather than a property of a spell itself). There are no clerics.
Going back to the earliest D&D rules, the D&D white box, we actually have cleric spells up to 5 and magic-user spells up to 6. The table even has a line showing the lack of cleric spells at level 6, indicating Gygax and Co. at least noticed this. Interestingly, clerics get 5th level spells at level 7, whereas magic-users (as they were called in 1st edition and earlier) have to wait until level 9, finally getting 6th level spells at level 12. Clerics also have no more than 6 spells per level, whereas magic-users have as many as 14 sometimes.
From the original description of Clerics: "Clerics gain some of the advantages from both of the other two classes (Fighting-Men and Magic-Users) in that they have the use of magic armor and all non-edged magic weapons (no arrows!), plus they have numbers of their own spells. In addition, they are able to use more of the magical items than are the Fighting-Men." They're an archetype now, but they were the original gish class!
So, the short answer is: they're not supposed to be as good magic-users as magic-users.
This model of clerics as half caster gish can also be seen in 0D&D clerics getting zero spells at 1st level (which carried over to B/X).This is what I would have said.
To reiterate what you said, in the Original you had Fighting-Men and Magic-Users. The class that incorporated both were Clerics. They weren't supposed to be as good of fighters as Fighting-men, and were not supposed to be as good of Spellcasters as Magic-Users. They were the middle of the two different types of characters.
The Illusionist, however, who has no combat capability and spells that only go to seven, is hosed.I suppose it helps to look at more than just cleric and wizard, though I should say magic-user here.
Look at the casters from Supplement 1 through 1e. There's cleric, druid, illusionist, and m-u. All of them, with the exception of m-u, go up to 7 spell levels. The m-u goes 9 levels probably because it's supposed to be the most powerful of the casters, like @Alzrius said. The m-u is also pretty much just the magic specialist, while the cleric had a balance between combat and casting ability. So traditionally the wizard is the exception, not the rule.
But on the other hand gets spells at 1st level that the magic-user doesn't get until 5th.The Illusionist, however, who has no combat capability and spells that only go to seven