No, if an iPhone is iCloud locked, you're not able to use the phone unless you enter the password of the account.

>if an iPhone is iCloud locked

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.

Yes, but your response doesn't make sense in context. GP specifically said that there are a lot of uses "for an iCloud locked iPhone", parent debunked it.

None of these work when the device is marked as lost/stolen.

This isn’t true. The iPhone is locked down over iCloud. I assume remote lockdown also works while the phone is turned off or on airplane mode (as Find My Phone does by using the passive Apple mesh network)

>I assume remote lockdown also works while the phone is turned off or on airplane mode (as Find My Phone does by using the passive Apple mesh network)

It doesn't need to be. If you have a passcode, the phone can't be used unless the correct passcode is entered. If you try to factory reset it, you can't get past the setup wizard if find my iphone was enabled for the phone prior to the wipe. Note this doesn't require that the phone receive notification that the phone has been marked stolen. So the only way you can use the phone is if find my iphone wasn't set up prior to it being lost.