If you drop a drop of sunflower oil on the surface of water in a wide vessel, then it does not spread

If you drop a drop of sunflower oil on the surface of water in a wide vessel, then it does not spread over the entire surface of the water, but forms an oil circle. Why?

After a drop of oil enters the water, it begins to spread over the surface of the water, gradually increasing the area S and decreasing the thickness of the olive layer n. So only the thickness of the layer reaches the size of one molecule, the expansion of the area will stop, because interaction forces act between the molecules. That is why a drop of oil will not fill the entire surface area of the vessel.