Just my thoughts,
We can't blame developers for doing this because of 2 main reasons:
1. ios users are statistically more likely to spend money on premium apps and iap because if you got money to spend on overpriced apple products, then you got money to spend on apps. Whenever I look at the premium version of an ad supported app, I only see that 10% of people from the free version actually bought the app.
Offtopic: btw this is why there are so many freemium apps; people just won't paid for premium app and end up paying way more for iap.
2. Since there are many variations of android kernels (e.g. touch wiz, sense, stock, etc) and screen resolutions on phones and tablets, programmers will need to spend much more time for an android version vs. ios version.
With that being said, developers are actually spending more efforts to gain less money on android while they spend less effort on ios and gain more money.
There's still hope: Ever since the GS3, and Note II became a huge hit, more ios users are switching to android which means developers will likely be developing games for android first, if not, at the same time.
Ahhhh, that was a mouthful..