Have you ever sat on a bench at the park or waiting for the bus or in any number of public places? Whether or not you speak to the people around you (or even actively observe them), you do tend to notice something about the way they are or what they are doing.
Maybe the boy sitting beside you is rolling a joint. Or that girl over there has on heels that are too high and a skirt that is too short. Did those two in the corner just exchange something under the guise of a handshake? And I wonder if that girl is old enough to be with the man she’s walking with!
Now you’ve seen it. You can’t unsee it. You can’t pretend that they’re not there and that it didn’t happen.