I know why! I remember a section in my hs sociology class that talked about this.
Westerners have a tendency to adhere to a very strict schedule. We all do it. We get pissy when the bus or the subway is late. We get docked for punching in/out late. Westerners live their lives by timetables. Free time is frowned upon (something spawned from the colonial era and is why we have so many after school programs in America - idle hands, the devil, old white Christian men that had sticks up their asses blah blah). Children often feel guilty about missing school, even if they’re sick. Dreams about being late to something are more prevalent among westerners. And so on.
This episode played on the fear of being late. Something as simple as missing the bus fills so many people with a dark dread in the pit of their stomach. The anxiety of being somewhere unfamiliar coupled with being late made for, quite frankly, one of the most upsetting and terrifying cartoon episodes of my childhood.