Remote start

Exhaust coming from a car gets your attention when you're biking - but more and more, I'm noticing that those cars are empty. "Remote Start" is running about a half dozen cars every morning along my 5 mile commute. This has been a warm winter in Minnesota, with temperatures rarely getting to zero (F, or 13 below C). It's certainly not too cold to bike. How come it's suddenly too cold to get into an unheated car?