system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How did popcorn become a standard movie "meal"?
gpt
Popcorn was originally sold by street peddlers.  Oftentimes businesses rented popcorn carts to poor / homeless people to sell popcorn on sidewalks around the city, in exchange for a cut of the day's take.  Unpopped popcorn isn't heavy or bulky, and cooking it requires simple equipment and little skill or effort.  Thus it's not surprising that popcorn would be a popular food in this role.

Movie theaters had to cut prices during the Great Depression because their customers didn't have as much money.  Meanwhile they noticed that popcorn carts seemed to appear outside at many theaters, because people liked to sneak it into theaters.  At the time, eating was forbidden because movies were viewed as an upper-class cultural experience -- eating at the movies would be like eating at a classical music concert.

So theaters decided that they needed re-brand themselves to be more attractive to lower- and middle-class customers by cutting prices and allowing food, then making up for the lost revenue by selling popcorn themselves instead of letting the street vendors get all the money.