It would still make a big difference where I live, where most phones are taken at gunpoint, and later sold for their screen, battery and shell if nothing else, unless you were walking down a particularly deserted neighborhood, in which case the muggers will make you unlock the phone and remove the passcode/fingerprint.

However, many don't know about iCloud/Find My Phone yet, and it requires an internet connection to disable anyway, which most people don't have outdoors, here.

Some kind of "fake mode," filled with random data, would also help with government coercion in, ahem, the more civilized countries.