Somewhere in the late 80s, or early 90s, our dairy industry mastered the production of milk in litre paper bags (like modern with milk / juice), but at the same time they were opened with your hands very easily: first you pull your nose to the sides on one side, then you pull out the resulting triangle and you can pour.
And after a couple of years suddenly started to pour the entire nose with glue so that without breaking the paper to open it became impossible.
And here’s how I remember now – my dad is standing over a newly opened package of milk, with a completely cracked paper nose in the process of trying to open, and to pronounce with a feeling of “aga, again we’ve got something optimized.”