They move. They have eyes that dart back and forth and blink and squint. They have mouths. They talk. They even eat. And they're outside. Outside. Can you imagine?
Sometimes their clothing is old. Sometimes they're sick. Last week one of them collapsed to the ground right there, and there was a great commotion, and an ambulance came and took the collapsed one away. Maybe that one even died. Maybe they all do, eventually.
What sort of existence could that possibly be? How could they possibly manage? It's not even worth thinking about.
They're not real. It's only common sense.