Question about supermarket herbs and vegetables packaging

Some supermarkets put things like . Like Parsley, green onion, rhubarb, Common Purslane, Nalta jute, watercress, chard, Fresh Chives, lettuce etc. In plastic bags, is this real essential for all of them. Which one of these really need this. Can lettuce for instance last long without doing anything to preserve it other than putting it in a fridge. submitted by /u/Background2005