Illinois is one of the states that has only recently enacted a "wine doggie bag" law. It is a good thing, I think, in that it removes the inhibition against ordering a bottle of wine (which is cheaper than wine by the glass) in a restaurant. There are some specifics about how the bottle must be sealed in a plastic bag by the restaurant. It is such a new thing here that neither restaurants nor patrons seem very accustomed to the idea, and I wonder how accustomed cops are to the idea. I think if I took the remainder of a bottle of wine home from a restaurant, I'd put it in the trunk rather than in the back seat of the car. Yes, supposedly it's legal, but if he's already stopped you for something, why give him something else to hassle you about? Have you met Chicago cops?
It's probably the lingering influence of my Depresssion-era parents, but I wash and reuse Ziplock bags too, at least once, anyway -- *unless* they have have had raw meat in them. If a Ziplock bag seems possibly not suitable for food storage any more, I can still find non-food things to use it for around the house: batteries, hardware bits, electronics, change, pencils, little bottles of travel shampoo and conditioner, etc.
I agree with Cloudship that sometimes in the US, saying you will take the rest of your food home has an element of politeness about it. The nonconfrontational among us (like me) take that route, rather than say no, I didn't care for it.
My dad used to moonlight as a bartender at a country club and would sometimes bring home really nice leftovers (steak or lobster) that a patron had forgotten and left on the table, even though the kitchen staff had packaged them very attractively in an aluminum foil version of a swan, for example. Oh now, if you're freaking out about my dad bringing home someone else's leftovers, I'll just say he was lower on the list than the younger, immigrant kitchen staff, and he did have nine mouths to feed.