Nobody on the planet needs 1000Gb of email storage, and anyone who offers it must know that. I could make the same offer to my clients - in fact I could offer them twice as much. Come to think about it, why don't I offer them a yottabyte, or even a pebibyte?
I could do so, sure in the knowledge that nobody will ever get remotely near the limit, and that's the basis of all these silly mailbox offers. The world's gone mad.