Why would society make "being a pedestrian" a crime? (Clarisse tells Montag that her uncle was once arrested for this.)

The people in control of society in Fahrenheit 451 want everyone to stay inside.... they want them to watch the walls, listen to propaganda, disengage from the world. Seeing a pedestrian might encourage someone else to go outside and take a walk.... possibly they'd have a conversation, and maybe...... that conversation would pique their curiosity..... make them want to learn something.