You are incorrect. Android applications can be compiled against purely Android libraries, or Google's additional libraries. The ones which do not depend on Google's services specifically can be used anywhere you like.
For example: There's a company running Android apps on iOS now.
How am I incorrect? I'm referring to the idea of an average consumer buying 100 apps for their Android device and then being leery about switching to iOS because they would lose those apps and vice-versa.
For example: There's a company running Android apps on iOS now.