Without an airtight seal you get increased spoilage. Something like 3% increased food spoilage might not sound like much but it’s equivalent to increasing the total environmental impact of farming, fishing, and food packaging industries by over 3%, which is massive.
Your ziplock bag is plastic, cheap non plastic containers aren’t generally airtight. A cereal boxes and similar items have a sealed plastic bag inside to prevent the food from going stale by the time you open it.
Sure a glass jar with a rubber gasket works as would a tin can etc, but they require a lot of energy and resources to make which means real environmental costs. Aluminum foil is one of the better options cost wise but it requiers a lot of energy and it’s even less biodegradable than plastic.
