James over at Grognardia asks, in the context of a module review, why there seem to be so many low-level adventure modules, compared to modules geared towards higher levels.
It's certainly a legitimate question, but one which I think lends itself to a relatively easy answer. First and foremost, it's the case that there are simply more low-level characters out there than higher-level ones. By their very nature, low-level characters tend to die, and thus there is a glut of lower-level adventurers out there needing low-level adventures.
Especially when a campaign is just getting off the ground, a game master using an off-the-shelf module makes a modicum of sense, especially when you don't know whether this particular group of tyros is going to be the one that makes it to mid-level, and thence to a very higher probability of survival.
It is also the case that higher-level characters tend, by the nature, to be well-ensconced in the particular campaign in which they have been playing. Thus, as a secondary factor, it's harder to design a "generic" module for higher-level play, given that higher-level characters are, by their nature, going to be more in tune with their surroundings, and thus their adventures are going to be, by and large, more setting-integrated.
That's not to say that higher-level adventures are impossible, or even difficult, to design. I've got a real hum-dinger waiting in the wings myself. But in terms of what is, and is not, published, I think it makes sense that there are more lower-level modules out there. They're simply more useful for what they are.