First: "ศัลยกรรม" means 'Surgery'. So don't use the word for those who have injection/other facial treatment. It's totally different. Although many women who got the plastic surgery are not afraid to tell but women who didn't have it won't like to be mistaken that they had it. Many people are still having a negative perception for 'Beauty Surgery' because, to them, it means Major change or Fake which lead to a 'between the lines" meaning that they are ugly. While those who only have the injection or other treatment feel like they only need a minor change. So you'd better not misuse it. "ทำหน้า" are more acceptable as a middle/blurry word for all the things. Some girls might use the term "โมหน้า" [ 'โม' is 'Mo' from 'Modify'] but it's more like a term for close-enough friends. Second : Many people (including me) have been taught to spend 'resource' thoughtfully and don't waste things. So if we have the chance to set the right quantity of what we eat, or if we can ... we prefer to leave nothing on our plate when we eat.