Remathilis said:3e's demographics are a response to a couple of fundamental questions...
1.) In a world of animated dead, crushing golems, powerful intelligent swords, and cursed rings, who makes all this stuff?
2.) Where were that PC (my best friend who just rolled up as a new character) before he joined our group?
3.) If guards kill orc raiders for years on end, don't they get the same Xp as I do?
4.) "Don't worry, I can steal every last coin from the mayor's vault. I'm 6th level, what can they possibly do to me?"
These are interesting questions, I see them come up all of the time, and I have a few problems with what seems to be the conventional wisdom. In order:
1. A 5,000 year old campaign world over time could produce plenty of golems, intelligent swords, etc. without all of those wizards existing in the current campaign year. Also, I don't think the DnD rules are such a simulation that there aren't other means for creating these items other than those outlined in the rules. This was especially the case in 1E, where demon lords and such could create items where no explicit power in their stat block gave them the ability to do so (just as no explicit power allowed them to grant cleric spells). It's a question of how complete you expect the rules to be - IMO the rules are geared towards those elements most likely to come up during the adventure - and a power that allows a demon lord to create an intelligent sword over time is not such an element.
3. A guard who is responsible for the death of more than one or two orcs in his career is an exceptional individual IMO. In any case I think the advice in 1E was that powerful characters would be more prevalent in dangerous areas. 3E doesn't solve this problem anyway because AFAIK there's no distinction made between peaceful and dangerous areas.
4. A mayor who can't deal with his local problems requests help from the local duke, who in turn would request help from the King. It's a natural result of stingy demographics that if 6th level thieves are that rare that the mayor can't deal with them, then 6th level thieves aren't common enough to cause problems in other areas of the kingdom, meaning the Duke doesn't have worse threats to deal with.
(Edit: Oh - also 3E sort of created a problem in this area anyway, because a CR 6 creature (like the thief in the example) is as powerful as two CR 4 creatures in theory. However, IIRC this was not the case in 1E - two 4th level thieves could probably kill a 6th level thief pretty easily. This means that large groups of low-level mooks were more capable of dealing with mid-level characters than they are now.)