Apple introduces the iPhone. Google follows up with the Android OS for cellphones. Apple introduces Safari browser based on WebKit. Google introduces the Chrome browser based on WebKit. Apple’s OS X competes against Windows. Google introduces Chrome OS. Forbes on why Google is stealing Apple’s ideas:
The parallels between Google and Apple appear to be a product of two different cultures: Apple is acting, and Google is reacting. And that’s why Google winds up stumbling into so many of Apple’s businesses. The two companies are accidental competitors. They just don’t seem to know it yet.
Brian Caulfield’s short answer: “Because they’re good. Long answer: because Google has none of its own.”