Popcorn wasn't always a movie theater staple. In the early days of cinema, theater owners hated popcorn because it was messy and the crunching sound distracted from the (silent) films. However, during the Great Depression, popcorn became a popular everyday snack because it was extremely cheap. Street vendors began selling it outside theaters, and customers would sneak it in. Realizing they were missing out on profit, theater owners began installing popcorn machines inside. During World War II, when sugar was rationed and candy became scarce, popcorn consumption surged even further. Today, popcorn has high profit margins, often being the primary source of income for movie theaters.