The problem is twofold: first, the target audience is smaller. Android simply hasn't achieved the global market penetration that the iPhone has -- at least, not yet. Globally, Android sales to consumers have totaled in the seven figures -- 5 million might be a reasonable guess -- whereas Apple's pushed another order of magnitude worth of devices, something on the order of 25 million iPhones, and if you tack on the iPod touch (which you should for the purpose of running these numbers) you're totaling over 30 million. Second, Larva Labs mentions a number of systematic problems with the Market -- teething problems that Google's yet to address -- including a lack of screenshots in app descriptions, a dearth of payment methods, the seemingly preferential treatment free apps receive, and a litany of miscellaneous bugs and issues (Android owners will fondly recall the inability to find updated apps a couple months back, for instance).
And now the million-dollar question, if you'll forgive our pun: will the Market get to the point where it's a logical business proposition for devs? In all likelihood, yes -- but it's going to take plenty of additional commitment from manufacturers, carriers, and Google itself to make the place a friendly joint for buyers and sellers alike. In the meantime, thanks to the wonders of modern capitalism, Android's app variety is fated to place a distant second, third, or fourth.
[Via Daring Fireball]