In the early days of food containers on the market, different types, shapes and sizes were available. There were steel containers, glass containers, food containers with lids, etc. Steel and glass containers were heavy enough to be carried for everyday use, while plastic containers had problems such as leaks and cheap plastic. Carrying cooked food from one place to another is a big problem. If you put it in a plastic bag and take it somewhere, there is a risk that the bag will leak, or the handbag or anything contained in it will leak. Can be ruined. Also, the food you eat loses its freshness and no longer gives you the exact flavor.