'Stepping Up To The Plate'.

Which plate, for pity's sake? Dinner plate? - Side plate? - Plate steel? - A trencher?
Why is this expression so much in evidence in today's spoken English?
Obviously, it could have nothing whatsoever to do with baseball as that is a largely American phenomenon to which we do not subscribe.
Can we not, as true English people, ditch inappropriate language: let us 'take a rain check' on it all shall we?
Perhaps readers would also care to follow me in 'going the whole nine yards' ???