It's not like they sit around and say: "Oh, f*ck Android, let's find vulnerabilities in other operating systems." I suppose it's long since they have a team working on Android vulnerabilities, but it's not trivial fixing, deploying - not to mention finding the flaws.
When it comes to others they have total disregard as to how difficult to deploy any fix is. The same standard should apply to themselves, but clearly doesn't.
They do offer a bug bounty for their own products, to encourage third parties to do to them exactly what they're doing to Apple and Microsoft.