I was also thinking about things supermarkets sell anyway, like batteries, lamps, cooking equipment, office supplies etc. which are in some sense also essential. Also the concept of essential can be dependent on the context. During a pandemic other things are essential than during a war like situation for example, also objectively. The real reason for not allowing shops to sell their full product range is because closed shops got envious, but on the other hand closed shops are generously subsidized by the state and even get a large amount of the missed turnover as subsidies in Austria.