Why do dead people look ghastly when they are embalmed?

Now I know that one reason is because they no longer sustain life (obviously). But when I say ghastly, I mean they even surp looking like a normal dead person would as in they look unreal like a waxed figure. The reason I asked this was because I recently attended the funeral of a friend of mine and what I saw in the casket was disturbing. She was 18 but she looked 48 and had a worried/frowning expression on her face. Also, her chest looked unusually bloated and stiff as if it were stuffed with paper or something and her mouth was sunk in. Her sister was traumatized by what she witnessed to the point where she had to be escorted out of the funeral home. Anyway, couldn't they be made to look somewhat decent and more presentable?