They won't; not directly. They don't need to either. Google is in the business of knowing their users. They make money by:

A) Knowing the make-up of your daily online life

B) Presenting ads that are relevant based on that profile

Android keeps you inside the Google ecosystem. Google search, Google mail, Google docs, Google RSS reader, Google shopping. Each of these utilities feed the core purpose of knowing you, which is beneficial to Google's bottom line. The better they know their users, the better targeted the ads can be, and the better they can convert.