Plastic lunch boxes stained with oil are always difficult to wash. Does this have anything to do wit

Plastic lunch boxes stained with oil are always difficult to wash. Does this have anything to do with the miscibility of organic matter?
The oily vegetables that are usually packed in plastic lunch boxes are particularly difficult to wash. Then I heard from a science student that this might be because organic matter is mutually soluble, but he didn't explain it clearly.

So is there a chemical reason why oily plastic lunch boxes are difficult to wash?

If it is really related to the miscibility of organic matter that he said, then when I eat the oil in the box, won't I also eat plastic? ? !