Because when the direction of such an important political and societal shaping decision, is supported (admittedly only by a small, extreme fraction of all of those voting Leave) but wholeheartedly by fascists the likes of Tommy Robinson, and when a Key supporter of the opposing view is murdered in the street in her own constituency, its only prudent and just to give people a final say.

An analogy might also be found in medicine, where clinicians, in offering treatment must ensure they gain fully informed consent. That consent is not absolute and can be withdrawn or varied at any time, particularly when new information. or circumstances arise. The world of finance often has something similar - that is, cooling off periods to allow a reappraisal of an important decision. So that people aren't ripped-off and 'taken-for-aride' by lies and spin.

It's interesting to detect the panic in the voices of those ardently supporting Leave, that they might suddenly lose the votes of a now much better informed voting population. After all, if the arguments are so sound and well made, what's to be scared of? Or is it that Democracy is good, but, hey we don't want too much of a good thing!