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Because they don't have a choice. Scenario: I need to buy some water or milk. I go to the market... what are my options? My grocer does not provide water in plastic or metal bottles, and no longer provides cardboard milk cartons. Scenario: I need a quart of oil for my car. Packaging options are: 32oz PET bottle. Scenario: I need a laptop computer. I order it online. There is no way for me to tell what packaging is us…
Short answer: buy less stuff. Longer answer: reduce your buying habits. Keep your laptop/phone around for longer before replacing it. Buy second hand or refurbished devices. Do you need to buy water, or could you drink (filtered) tap water? Do you need to buy milk, or can you replace it with an alternative? Soy and oat "milks" are different, but serviceable replacements. Avoid almond and other nut "milks". Sometimes…
The global solution to reducing plastic packaging is to reduce the use of plastic packaging, mostly by using cardboard and glass instead. That's driven by manufacturing, not consumer action.