In short, the types of things that players want are bad for the game. They'd be fine if published in moderation, but moderation is a luxury only small companies can afford. Big companies have big monthly bills. The types of supplements that would be healthy for the game, players won't buy in sufficient quantity to keep the company or the game alive at the corporate level. To keep the engine running, the company must publish what customers want, and thereby cut its own throat.That's as true a statement about D&D thirty years ago as it is today.
Anyway, head on over to his blog and take a look at what he's got to say. Having been involved with D&D as long as he has, I think he's got quite a few insights to share. I interviewed Mr Winter back in 2009, in case you're keen to learn a little more about the man and his involvement in both the hobby and the industry.