Very few people "just watch" a movie anymore. The majority watch a film on their TV while scrolling Twitter on their phone. As a result, entertainment content is being designed for "background listening"—exposition is repeated, dialogue is slower, and visual subtlety is lost because the audience is distracted.
Short-form media exploits the variable reward schedule. You scroll because you don't know if the next video will be hilarious, shocking, or informative. This unpredictability keeps the brain hooked. Popular media has evolved from satisfying storytelling to interval reinforcement.