Someone made a comment in one of the great multi-classing debate threads that Gygax added dwarves and elves primarily as an option for players who generated substandard ability scores, gaining some special abilities right up front in exchange for not advancing as fast or as far. I've never heard this before, and I'm not sure that it was true, but it's interesting to contemplate.
Start with the way human characters work. You get theoretically unlimited advancement, with special features gained at name level. If you have a high ability score, you get to that goal faster. Therefore, if you roll 3d6 in order first, then choose your class, you can either go with the class you'd be best at, or with the class that you find more interesting regardless of the actual score.
If you roll badly, though, you won't have a choice between fast advancement and more interesting. At this point, the races come in as options. You can play a substandard fighter (dwarf) in exchange for some useful dungeon-delving skills (very useful in the original game, since they were all automatic, originally.) You also get a saving throw bonus. You could instead play a substandard magic-user, but with the ability to use a wider range of weapons and eventually wear magic armor while casting spells. Either way, you have to give up the option to reach name level.
Later editions in both the Classic and Advanced lines screwed this up by introducing minimum ability scores, not only for each class, but also for the races, plus the level cap is linked to an ability score, which kind of waters down that concept. The thief class also disrupts the idea a bit, since thieves are not level capped for any race.
If a conflicting story I heard is correct, then the Greyhawk rules were actually already in play before the publication of the original booklets and were divided up into the core booklets and the first supplement, simply because there wasn't enough room to include everything in the three booklets as planned. That means the thief was already in use, which makes the claim that dwarves and elves were intended to placate players who rolled badly a little less likely.
But I'm wondering what the races would look like if they were explicitly re-designed to meet that goal.