A few remarks:
1) Personal biases: I love HERO, I love D20, and I hate GURPS (too many internal inconsistencies).
2) Where are the modules? As has been pointed out, they're out there, just not published in great numbers by WOTC. Look to Dungeon and the 3rd party publishers. (BTW, Judge's Guild is still out there somewhere...) Let's not forget all those mini-modules that were released- I don't know what kind of profit margin those had- they were mostly bad but some were excellent. In addition, the trend of DM's doing their own homebrew has strengthened, so any module on the market is competing not only with published, internationally distributed products, but also with thousands upon thousands of people writing their own stuff, some of which winds up online. And that doesn't even address the issue of the extant, unconverted 1Ed & 2Ed adventures, not to mention conversions of excellent adventures from other games! In terms purely economic- there are too many substitute goods for there to be much profit in printing new D20 modules.
3) In addition, as you point out, the quality of some of the new modules is, well, subpar. This will drive the demand curve down- in other words, people will be less desirous of modules in general because there is a general perception of a lack of quality. If people think their homebrew is better than a module from the store, they won't buy it. If they won't buy it, modules don't sell, and wind up in the discount bins. Eventually, modules stop selling to their breakeven point, and modules die as a commercially viable product.
1) Personal biases: I love HERO, I love D20, and I hate GURPS (too many internal inconsistencies).
2) Where are the modules? As has been pointed out, they're out there, just not published in great numbers by WOTC. Look to Dungeon and the 3rd party publishers. (BTW, Judge's Guild is still out there somewhere...) Let's not forget all those mini-modules that were released- I don't know what kind of profit margin those had- they were mostly bad but some were excellent. In addition, the trend of DM's doing their own homebrew has strengthened, so any module on the market is competing not only with published, internationally distributed products, but also with thousands upon thousands of people writing their own stuff, some of which winds up online. And that doesn't even address the issue of the extant, unconverted 1Ed & 2Ed adventures, not to mention conversions of excellent adventures from other games! In terms purely economic- there are too many substitute goods for there to be much profit in printing new D20 modules.
3) In addition, as you point out, the quality of some of the new modules is, well, subpar. This will drive the demand curve down- in other words, people will be less desirous of modules in general because there is a general perception of a lack of quality. If people think their homebrew is better than a module from the store, they won't buy it. If they won't buy it, modules don't sell, and wind up in the discount bins. Eventually, modules stop selling to their breakeven point, and modules die as a commercially viable product.