<i>Today, no one will choose to use iCloud over Google apps</i><p>I do. The only Google service I actually use anymore personally is GMail but that simply forwards to my iCloud account. It's easier and more efficient on battery to just check one mail account. I also ditched Google Calendar / Contacts for iCloud because they work almost exactly the same. Again easier to just use/sync one service IMO. I was never a big Google Docs user to start with but now I use DropBox and native apps. Again I only setup my DropBox once and it's good to go. I can use different (and more powerful) apps as needed. Sometimes Numbers on iOS is fine for quick data entry but for building out a big spreadsheet I'm going to most likely use MS Office on a desktop. I guess you could do this through Google Drive now but I already have DropBox setup so why bother? I use FaceBook/Twitter instead of Google+ which are both first class citizens on iOS/OSX now. FaceBook chat has replaced GTalk just because everyone I know uses it. A lot of this goes back to Google's period where they did a very bad job supporting iOS. The path of least resistance was just to use something else and now I have no need to switch back. From what I've heard their iOS apps have improved greatly but I'm happy with what I'm using.
The vast majority of users don't care if they use Apple of Google apps most of the time. Even maps which was a big deal among us techies, most of my regular friends couldn't care less which apps they use. And for many, facebook has largely replaced email anyway.
iOS has had the ability to share keychain items between apps from the same developer using 'keychain-access-groups' since iOS3. Google could use a single login for all their iOS apps, but they probably have a host of reasons why they do not.
This is already possible if they have the same Bundle Seed ID.<p>This feature has been around for either the entirety of or damn near the entirety of iOS programming.<p><a href="http://developer.apple.com/library/ios/#documentation/General/Conceptual/ApplicationDevelopmentOverview/ConfigureYourProject/ConfigureYourProject.html#//apple_ref/doc/uid/TP40011186-CH6-SW8" rel="nofollow">http://developer.apple.com/library/ios/#documentation/Genera...</a>
Google itself might not want iOS to have this feature. If they can keep their apps sufficiently far ahead of Apple's, power users will use them in spite of the extra hassle. Some of those power users will feel like they're getting a second-rate experience with iOS and might switch to Android. If they could functionally swap native iOS apps out for Google apps such that there's zero hassle to using them, iOS power users would feel like they had the best of both worlds and have zero motivation to switch platforms.<p>Power users certainly aren't the majority of the market, but they do tend to steer things. There are, of course, <i>many</i> barriers that keep users from switching platforms, but every little bit helps.
This isn't an issue of Android being more "open". Google baked-in one-sign in features into Android, sure, just as Apple did with iCloud. But you <i>can't</i> do this for other 3rd party apps on Android. You can't sign in on one app, and continue being signed in on another app (at least not in the way that you complain Apple should allow).<p>I do like your idea, and agree Apple should allow this. They should also allow changing the default applications, and allow better access to internet APIs, so Mozilla can actually make Firefox for iOS. But that aside, what you're complaining about isn't something Google does either