1. Hygiene - It is use and throw - there is no reuse - so you are ensured of hygiene and cleanliness. The leaf can be used only when it is fresh, so no question of "Old stocks". It is quite easy to grow a banana tree in the home - one can harvest a leaf just before a meal to have a very fresh leaf for the meal.
2. Medicinal properties - When hot food is served on the banana leaf, the food mildly absorbs the antioxidants and other friendly chemicals from the leaf and transmits it to the body in very small doses. These anti-oxidants are similar to what is found in Green Tea. So they enter the body effortlessly and work to prevent any stomach disorders, and prevent various other ailments.
3. Since its a use and throw, there is no need for post-meal washing - so no usage of soaps or water - how better could conservation become.
4. What happens to the used leaf? You can dump it in a nearby open space. If cows are sheep are in the vicinity, they will have a quick snack, if such bovine animals do not frequent the place, the leaves will decay and mingle with the soil in just a few days' time.
Once you plant a banana tree, it also gives rise to shoots of new baby banana trees, hence, they live on for ever, provided you give them space, and some water.
Hail our culture for influencing our lives in subtle but powerful ways.