Why do people say supercalifragilisticexpialidocious?

Oh, dude, people say supercalifragilisticexpialidocious because it's like a fun Word from that Mary Poppins movie, you know? It's just a way to sound all fancy and make people go, "Whoa, that person knows big Words!" But like, it's not like people actually use it in real life conversations, unless they're trying to impress someone or win a spelling bee or something.