Comment by Sophira

I would imagine that this serves the same purpose as the way that early home consoles would check the inserted cartridge to see that it had a specific copyright message in it, because then you can't reproduce that message without violating the copyright.

In this case, you would need to reproduce a message that explicitly states that it's Google's copyright, and that you don't have the right to copy it ("All rights reserved."). Doing that might then give Google the legal evidence it needs to sue you.

In other words, a legal deterrence rather than a technical one.