First, it makes your vehicle a prime target for an opportunistic car thief. In fact, one of out every eight vehicles stolen in 2015 had the keys or fob left inside. That can cost you a few hundred dollars to thousands of dollars depending on your level of theft insurance.
Second, in an effort to reduce unnecessary thefts, many states and municipalities have passed laws banning "puffing." It's illegal to leave the car running and unlocked, even in your driveway. Remote starters that allow you to start the engine while the car is safely locked up without the keys are usually considered a safe alternative.
"Getting a warning or a ticket is preferable to having your car stolen," said NICB President and CEO Joe Wehrle. "As we've reported previously, 57,000 vehicles were stolen in one year with the keys left inside. That's one every six-and-a-half minutes. And when you add up the costs of replacing those vehicles, it's hundreds of millions of dollars. Many of those cars are not insured against theft and the owner is left holding the bag and paying for a new car."
NICB recently produced new public service announcements related to this issue and they are now airing on media outlets around the country. Here are the links to view them: Leaving Your Keys in Your Vehicle and Warming Up Your Car.
To view a list of states where it is illegal to leave a vehicle unattended while running click here.