Not all states require rear passengers to be buckled in, which is why all drivers should get into the habit of making sure their passengers are using their seatbelts. After all, parents wouldn’t think of driving anywhere unless their kids were safely buckled in, and so it isn’t logical to assume that adult passengers would be any less at risk during a crash.
You can learn about the risks of unbuckled passengers when you watch this video. You’ll learn that, even at low speeds, a crash will send an unbuckled rear passenger flying forward into the driver’s seat. This can cause the buckled-in driver to be propelled forward into the airbag. Drivers are about twice as likely to be killed in a collision when the passenger seated behind them isn’t wearing a seatbelt.