[duiker101]

It's not the actual selling of the device the problem, it's the way you are locked in the walled garden. Let's say, you don't like the next iPhone. You want something different. Well, tough shit, you will need to find a new way to store all your photos and files since you won't be able to use those either on any other device. Same goes for anything else you might have in your iCloud.

Now, I'm not saying that you can't use other services or anything, all I'm saying is that if you put all your eggs in one basket, it becomes hard(not impossible, usually, just harder) to then move them away.

[GeekyBear]

Again, using the iOS version of Google drive to back up the iPhone would back up all the photos, videos, contacts, and calendars.

All the user would need to do is sign into their new Android device with the same Google account they used to backup the iPhone.

Copying user files from iCloud Drive to Google drive (or any other cloud storage option) is likewise extremely simple.

I'm not aware of any lock in that isn't related to apps that aren't available on both platforms.

[skinnymuch]

You just move everything from iCloud over to something else. I don’t see where any lock-in is for what you’re describing.