Why would you bake in the ability to disable things like network access when ad serving is the main source of revenue for app developers?
Because Google screwed up early on. When Android launched, Google Checkout (now Google Wallet) was available in too few countries. Paid apps would not appear in the Android Market (now Google Play Store) application, and in the web, they would appear as "Not available in your country". So in order to get any sort of international user base for an application, the developer had to distribute it without charge. This led to a culture where users expect free apps. Apple, on the other hand, never launched the iPhone or iPad in a country until it had payment working in that country.