I always thought of it in primary school terms.
If there are 6 sweets, and two people want them, they get three each.
If there are 6 sweets and no one wants them, then you can't say how many each person gets, because there are none, but you can't say they get no sweets each, because then the original 6 won't be given to anyone.
That makes less sense than I thought, but oh well.