how much insentive do they need?
From the discussions I've had, a lot more.
They can develop an app for the iPhone, charge 59p for it and see it sell in its thousands, if not tens of thousands. Develop the same app for Android and they'll see hundreds - if they are lucky.
Release an app for free on iPhone (most of which generate revenue by some other means) and you'll start to see people picking up your paid apps on the strength of your free apps. Release an app for free on Android and you'll be extremely lucky if it's ever seen again amongst the complete dross that's flooding the Market.
The more common complaint is that the implementation of the Market for Android is pathetic, both on the handsets and on the web. iTunes walks all over it in every possible way and gives its users what they want - a simple, easy way to navigate the various apps and see what they can do.
I applaud Google for it's open-source approach to apps and but there's a thing as too much choice. Until someone starts sorting through all the apps and displaying them in a logical manner, Android will never be able to compete with the iPhone and devs will continue to code for the platform that has the most potential customers. There also needs to be some drastic QC implemented somewhere along the line.