A lot of app developers 'cut their teeth' on iOS aswell. And I know a couple of friends in the app development field who won't consider developing for android, since essentially all android users (me included!) want apps for free, whereas apple users are so used to paying for everything extra (my take on the situation ) that they feel happy to pay for an app. I think a friend quoted that you need to have 10-100k downloads of an app before it even approaches profitability.

Having said that, the examples you cite aren't wanting to make money from selling an app, so the other reasons above are probably just as valid.

tb