Ridley's Cohort said:Karinsdad,
You are forgetting a big piece of the puzzle: humanoid NPCs.
Certain kinds of magic items are more likely on the basis that they give good bang for the buck, as well as being an easy method of improving that character's forte.
If dead NPCs are not regularly providing these kinds of items, it means they are probably somewhat underpowered. That is not necessarily a bad thing as the PCs are also underpowered relative to the guidelines. But it will hit the NPCs proportionally harder because PCs have more ready access to animal buffs, Protection vs. Evil, etc.
This begs the question:
How much stuff do you give to NPC humanoids?
Do you give every NPC humanoid the same equivalent GP value of magic items that PCs get? For example, 19,000 GP for every 7th level NPC opponent?
Obviously not. Otherwise, the PCs would quickly acquire more magic items than the wealth by level table indicates.
But, with 13 encounters per level and maybe 25% of those against humanoid NPCs, that would mean that each humanoid NPC (assuming 4 of the same level per encounter) would have on average 1/13 of the DELTA of the wealth per level of the PCs and at most 4 * 1/13 of the delta (i.e. all magic item wealth is acquired by NPC humanoids).
So, a 7th level party of PCs facing off against a 7th level party of NPCs should encounter between 1/13 * (19,000 GP - 13,000 GP) = 461 GP on average and 1846 GP at most per NPC. That means that most 7th level NPC humanoid opponents could not even afford a single +1 magic weapon, let alone an ability score boosting item. The entire NPC party of four might only be able to afford one or two magic items.
They might more easily be able to afford a +1 Longsword (at 60% of the cost of a +2 ability score item) or a +1 Shield (at 30% of the cost). If you were an NPC BBEG, would you hand out one +2 Strength item at 4000 GP to your minions, or two +1 Longswords at 4630 GP, or fifty +1 arrows at 2000 GP?
With economics and plausibility in mind, wouldn't ability score items (especially ones at +4 or greater) be extremely few and far between? Sure, the BBEG could (or even should) have one in his main area of expertise, but beyond that, shouldn't they be rare?