Earlier quoted context omitted.
On a somewhat related note: why do browsers allow websites to prevent you from leaving via those annoying dialog boxes that ask you to click "cancel" or "leave"?
I have seen sites that have pages where you're placed in a queue (for whatever reason) and if you leave the page you will be dropped from the queue, so it's nice to have something preventing you from accidentally leaving, but that's the only legitimate use I can think of.
Of course a better solution wouldve been a program which doesnt so easily let you lose data in the first place, but this software was long past that.