This is influenced by the popularity of Japanese TV series. At that time, many male and female protagonists would start their dating and meeting by having lunch together and eating a "lunch box", which is what we usually call a "box lunch box" or "lunch box". Because Japan called this kind of portable food box "bento" (transliteration is "bento"), with the gradual cultural integration, "bento" became synonymous with "fast food". Just like "taxi" instead of "taxi".