America The Unsocial

I find it funny that in America, it is socially acceptable while someone else is filling up their cup at a soda fountain to:
1. Get ice from the center ice dispenser
2. Get soda from the opposite side of the person originally filling up their cup.
But, it is NOT socially acceptable to get soda from the same side as the original person at the soda fountain. They get all bent out of shape and feel like you're invading their "intimate zone" if your soda cup is next to theirs. As if the soda cup is an extension of their personal zones. Ridiculous.