Each country has their own grocery packaging habits. In the US, generally in supermarkets there is someone whose job it is to package your purchases. Generally the feeling you get if you are in a rush and try to help is that putting stuff in bags is a science and no one but professionals are qualified. You should not even try. This is actually somewhat true. Generally although you can pack a few 2 liter bottles of soda in to one bag, you should avoid this because it will be too heavy, so you match Soda with say Pringles (c), which has the same shape but weighs a lot less. You should keep cold things together and avoid mixing things that cannot get wet with things that form condensation. And on and on. Ask anyone who does this for a living. You'll find out all you need to know, and more.
This is knowledge that no American finds useful, because we have people who do this for us. But, I remember some ten years ago being in a grocery in Israel. I brought all my stuff up to the counter and paid, and then just stood there waiting, until the woman asked why I wasn't putting anything in a bag. So I packed up my stuff (really poorly) and took it home. I pitied anyone who was new at this and was buying eggs. Back then they did not even give you cardboard or Styrofoam containers. Actually I am still not sure how they did it. They have improved drastically since.
Here in Germany (I think I remember this in Switzerland too, but I forget) there are a few options. In big supermarkets you take your stuff up to the counter and pay for it, and then you take a bag from the box and the guy looks at you in a really mean way and tells you that he had no idea that you were going to take a bag, and that he forgot to charge you for it. So you end up paying an extra EU .50 for two bags. Then of course you have to package it yourself. In a bakery they separate each thing you buy and put it is a small paper bag. Then you collect them and carry them home. In general you are supposed to bring your own bags to these things. So people will come with all sorts of carrying contraptions to stores. This custom goes back about 10 years to a debate in Germany as to how they want to handle the environmental issues that affect us all. They decided to charge more for bags. (This of course explains why they think that the pittances of the Kyoto Protocols would be remotely useful. They thought that by eliminating bags they will save the planet. There is no notion that the sacrifice should be proportional to the benefit.) I do admit however that this might not be a bad free market approach to the problem. But I don't really see this making much of a dent. I mean it could have been worse, they could have outlawed plastic bags altogether.
(Oddly enough, when I suggested getting rid of straws in bars, and drinking cocktails straight from glasses, in order to now waste plastic on such things, people looked at me like I had suggested abandoning the concept of underwear. Go figure.)
The only place that you get packaging and bags is the small groceries that are generally operated by immigrant Asians. When they ring up your purchase they will ask you if you want a bag. If the answer is no then they will just give you a price and you pay and take your stuff. If your answer is in the affirmative they will give you a bag and put your stuff in it as they tally the price. These groceries are also open as much as the law lets them get away with. It is quite civilized.