Starrylizard

They exist and are enforced pretty rigorously (e.g., the Texas Department of Public Safety's "Click It or Ticket" campaign); you might not get stopped for not wearing your seatbelt, but the charge will likely be added to your ticket if you're stopped for any other reason. TV shows are just unrealistic that way--though there's a case to be made in SPN for the Impala not having seatbelts because it's an older car.