Hello,
The eminently organized Swiss have been using bags and jugs forever, and the jug can be exactly the same size and shape as a carton, and therefore fit in the fridge door shelf. Bags are a very reasonable form of packaging, although see-through is not a good option, as milk is light-sensitive.
However, in Mauritania, and maybe other poor countries, most people don't have fridges, or can't keep anything in them owing to large families, so they buy milk for immediate consumption - 0.5 or 0.25 litres. The real problem was "suckling" the bag, felt as undignified. Besides, drinks are served in social settings together with sodas or fruit juices, on a tray, and cartons look so much nicer.
We thought that cultured milk, which is used to mix with water and serve in a collective bowl (or jug nowadays) would be opened in the kitchen, and therefore a bag would not be a problem, but it still was not accepted.
Best regards,
Nancy