Most of out food comes packaged so except for loose produce, contamination is not much of an issue, certainly not with anything prewrapped, in cartons, bottles, boxes or cans.
But loose produce will always be an exception, needing a new plastic bag, and the only worry would be the migrant worker who schyt in the field next to your lovely red lettuce.
Drippy meats will always need special care and fresh plastic. Same with fresh fish.
So there will always be a need for a combination of reuseable and easily recyclable or biodegradable ways to get food home. Part of my battle is won with a cardboard box that opens into my "granny cart" and cans, boxes, cartons, bottles etc just get dumped in the bottom. Perishable and frozen stuff goes into old plastic bags.
But I think styrofoam is a special case whose banning would be a terrific idea. (As I sit here sucking my coffee from a styrofoam cup.) As soon as I get rid of these Goddamn taxes, I'll see what Macy's has to offer. Do you think the clerks will mind if I put my mouth on all their cups?