It's not just hubris or marketing. Apple fans like to see apple UI guidelines followed on Apple devices, and Android fans like to see Android design guidelines

It's not just hubris or marketing. Apple fans like to see apple UI guidelines followed on Apple devices, and Android fans like to see Android design guidelines followed on Android, but the normal non-technical users who don't really care expect facebook to work the same way on their android phone and their iPad and their work computer. People don't want to have to re-learn how to use the wal-mart app after their grandson convinces them to give up their old Galaxy S3 and buy the new iPhone. Expecting all apps to obey the platform guidelines is just as much hubris as ignoring the platform guidelines is.