Yep, that's what I thought too, but had no way of confirming it.
It can also be that they wanted citizens to cultivate more of it in their home gardens for its nutritional values. But either way, I have no data to confirm it.
>>ahmedf+(OP)
Hell, it could have been a stupid reason. Maybe someone actually thought carrots improved vision; maybe someone just thought it was hilarious to make people thinks that; maybe someone needed another poster to make to meet quota and ran out of ideas; maybe someone had a bet on whether they could get a carrot campaign approved.