Why do boys and girls admire female scrawny heroines in movies and computer games and also TV when really in real life they lack power and strength

First of all, none of those women are scrawny, look at Wonder Woman, she was skinny and well-shaped sure but she was far from scrawny. And skinny women do not lack power or strength, some of the most powerful women I know are extremely skinny. Don't stereotype, it doesn't make anyone happy.