Earlier quoted context omitted.
I disagree. There are a lot of uses for an iCloud locked iPhone, such as a music player, podcast player, security camera, etc. Edit: I should clarify that the embedded video clearly showed that a number of the iPhones she had were still able to be used. Perhaps the owner didn't or wasn't able to iCloud lock them, but that's what I originally meant.
No, if an iPhone is iCloud locked, you're not able to use the phone unless you enter the password of the account.
but that still leaves the possibility that it isn't locked, and therefore it is worth it for theives to steal it. Even just the chance that it's not locked would make it worth stealing.