So how long were you waiting in line at the bank drive-thru?
How many cars were waiting in front of you? How long were you actually waiting before it was your turn? Was your car running continuously while you were waiting there?
Did you leave your car idling, while quickly running in to get your dry-cleaning?
How about that railroad crossing that you had to stop for because a mile long freight train was going by.
Believe it or not while your car is idling (and not going anywhere) you were still using gas. Unless you drive a hybrid that is in electric mode at that time, you get zero miles per gallon when idling. Depending what you drive your can use anywhere from half a gallon to a full gallon of gas per hour of just idling. In addition you are still sending CO2 and othere noxious emissions in the atmosphere.
Ok so let's see how idling affects your car's engine: While you are idle (not driving, but engine is on): You put unusual wear on the engine as the car does not cool well. At higher temps engine oil breaks down faster. This in turn requires more maintenance intervals. With the oil running at higher temps you are also putting additional wear on the engine components.
As you can see long term idling may be convenient for you, but harmful to your wallet and the environment.