Ireland's call?

Watching the sport on television yesterday, my grandson asked why Ireland play rugby as one team, but football as two. Good question and I'm not sure there's a definitive answer. Both association and rugby football of course well predate the partition of Ireland and therefore originally both codes would have had Ireland playing as a single entity. So perhaps the question is not so much why do they play as a single team at rugby, as why don't they at soccer? And the answer seems to be that whereas there was no real enmity in the pre-partition years between the rugby sides of north and south, there was as far as association football was concerned, and so following partition they took the opportunity to form two separate organisations, whereas rugby didn't bother.