Level in d20

In previous editions of D&D, high level characters were something to be treasured, having been built up over lots of time. Most of the DM'ing advice that was seen was that characters should start at 1st (occasionally 3rd) level and be built up from there. There was a feeling that if you started at higher level, you were somehow cheating. Moreover, high level characters became something for DMs to fear, as they were so capable.

In 3rd Edition, and in other expressions of d20 (particularly d20 Modern), this is no longer the case. The game is not perfect, but it is now playable across a much wider range of levels. And, high level characters are no longer something to be feared.

This expresses itself most clearly in NPC design. In 2nd Edition, 95% of the populace were thought to be 0-level humans. Even 1st level characters were supposed to be quite rare, and 5th level characters were unheard-of, except for the retired 12th level Fighter behind the bar, of course.

In 3rd Edition, there's a tendency to slip into the same thinking. Virtually all NPCs remain 1st level commoners, with squads of higher level guards distinctly unusual. Thus, even mid-level PCs become unstoppable, since DMs remain unwilling to have the king's elite guards be high level, when they most likely are in a 'realistic' setting.

Of course, this doesn't make the 20th level Commoner any less ridiculous, nor the fact that tending farm will necessarily improve your ability to fight.