Supermarkets trying to distract our attention with initiatives on plastic bags when the real problem is the enormous amount of excess packaging housing their products.
If supermarkets could use less packaging they would. It all comes down to cost, how much they charge you, whether the product will reach its destination in good condition etc. Less packaging is generally cheaper. Packaging in cardboard and environmentally friendly, compostable and recyclable packaging is better too. Choose paper/card over plastic if you can.