Multiple companies are involved in getting these things out and it takes longer to set up than having one company control everything.
There's a lot of marketing dollars at work with android and the network effects of the users will ramp up. The first generation of androids were ugly and inelegant compared to the iphone but the next gen looks better thought out and prettier inside and out.
Like Wayne Gretsky said, "Skate to where the puck will be"
Launching a cool app on Android first will get you a lot of press. There's just less competition there. There are tons of well read bloggers and journalists who would be very interested in your Android App and the people marketing the phones would probably feature it in their ads like apple did with the "There's an app for that" ads. That's how marketers think. "It worked for Apple, so we'll do it too."
Going to the iphone first will probably take two weeks to a month to get approved while the Android version can update faster with less hassle. You get to iterate faster and get feedback on the latest results. A faster feedback loop is essential to iteration and improvement.
After you get some attention, then you can make an iphone version and if you're a top 5 Android app, that's a good reason for people to take a look.
In the history of software, I'd say look at Microsoft Excel. It launched on Mac which had some crazy new features like a GUI. It quickly became the top spreadsheet on the mac (there was little competition). Launched on Windows a couple years later and went on to dominate the category.
Of course, the flip side (as a lifelong Cubs fan) is that Android developers may be eternally chanting "wait 'til next year". It seems like the big moment for Android is always just around the corner, but never actually arrives.
At those conversion ratios, it goes without saying that a thousand birds in hand is worth a whole lot more than one in the bush.
If it had come a month and a half ago Verizon could have saved me a switch to T-Mobile!
Hard to find paid apps (We suspect Google would rather just have everything be free since they default most views in the catalog to free apps, or top downloaded apps which means free apps. The option to show paid apps is buried in a submenu.)
How many users do you think ever saw that sub-menu, much less clicked on it? Yes, Google would rather have apps be free. So would Apple. Why? Because smart companies try to commoditize their products' complements [1].
This really really sucks for people whose business model is "make money selling an Android app", but personally, I think that's a really crappy model to begin with, be it on Android, on the iPhone, or on desktops. Just make your app free and find another way to make money.
1. http://www.joelonsoftware.com/articles/StrategyLetterV.html