More people have iPhones than Android phones in the U.S., but globally, Android claims a 72% market share, according to Statcounter. Releasing Android apps significantly expands Apple's market.
Apple's Services business is its second largest behind iPhone sales, and Services hit a $100 billion per year revenue rate last year. In addition to subscriptions like iCloud, the unit also includes sales from advertising, search deals with Google, AppleCare warranties and payment fees from Apple Pay.