Level limits for the fighter class(es) kind of make sense since all of the demihuman races (including, in 1E, half-orcs) are smaller than humans and have lower maximum strength, so it seems reasonable they’d have a lower maximum hp cap, and the smaller the race the lower the cap (halflings and gnomes severely limited, elves and half-elves less so, dwarfs and half-orcs barely limited at all). That said, there’s no real reason they couldn’t continue to improve their attacks and saving throws even if they’re no longer gaining hit points (which BECMI sort of did with its Attack Ranks kludge).
Level limits for demihuman spell casters are harder to justify, and it’s really just a taste/flavor preference that Gygax wanted the highest level spells reserved to humans and for demihumans to exist in a secondary or supporting role - that they’re better for casual or younger players since they have a lot of “instant gratification” special abilities that are most useful at low levels, but the more serious and strategic-minded players who are thinking in the long term would (presumably) forego those shiny trinket abilities in exchange for unlimited potential.
It didn’t really work out that way (especially as the level limits kept being increased from OD&D to Greyhawk to AD&D to Unearthed Arcana to 2E to the point where most campaigns were never going to reach levels where they became relevant) and probably should have instead been dropped and replaced with something like requiring demihuman characters to earn 1.5 or 2x as many XP to level up as humans (alongside a maximum HD cap), which IIRC was presented as an optional rule in 2E.
I suspect they would’ve gotten there eventually even if Gary remained in charge longer (he was a LOT less wedded to the cobbled-together sacred cows of the 1E rules than a lot of the modern-day 1E grognards).
Level limits for demihuman spell casters are harder to justify, and it’s really just a taste/flavor preference that Gygax wanted the highest level spells reserved to humans and for demihumans to exist in a secondary or supporting role - that they’re better for casual or younger players since they have a lot of “instant gratification” special abilities that are most useful at low levels, but the more serious and strategic-minded players who are thinking in the long term would (presumably) forego those shiny trinket abilities in exchange for unlimited potential.
It didn’t really work out that way (especially as the level limits kept being increased from OD&D to Greyhawk to AD&D to Unearthed Arcana to 2E to the point where most campaigns were never going to reach levels where they became relevant) and probably should have instead been dropped and replaced with something like requiring demihuman characters to earn 1.5 or 2x as many XP to level up as humans (alongside a maximum HD cap), which IIRC was presented as an optional rule in 2E.
I suspect they would’ve gotten there eventually even if Gary remained in charge longer (he was a LOT less wedded to the cobbled-together sacred cows of the 1E rules than a lot of the modern-day 1E grognards).