Yep, otherwise they don't work. Cardstocks don't hold milk, sterile. Pure aluminum cans dissolve into food contents. Glass lids can't seal tight enough.

Food producers and public health authorites has food poisoning lawsuit and human safety at higher priorities than environmentalism. So they just make it all packaged up in plastics.

Doesn't mean some sort of waterproof inner wall coatings can't be made in the future, though. Maybe if we substitute PE with engineered PLA made from agri wastes and made sure to burn it, that could make sense someday.

truly this. you start deconstructing packaging only to e.g. realize they've glued LDPE into the inside of an otherwise fully recyclable item to make it look slightly better in stores for longer due to moisture.

This is true. But it's worth noting that in terms of mass, it's a lot less than regular plastic packaging as these are very thin coatings. But you are right that this is not a perfect solution. I'm guessing there might be some biodegradable alternatives though for some of these things.

At least cans are being recycled in parts of Europe now. You pay a little deposit when you buy cans of beer/soda and you get that back when you return it. I'm guessing the plastic just burns off when they melt the metal. Even regular cans without a deposit that go in the trash are being separated out probably and recycled.