Key gets stuck in ignition

Yesterday for the first time ever, my key would not turn the engine on, and it was stuck in the ignition without me being able to remove it or turn the car on. I am not sure if the wheels were turned while it was in park in the parking lot, but I am pretty sure I did not leave the steering wheel in the lock position. I called a AAA technician out to help me, and he sprayed WD40 into tumbler with key in it, and also lightly tapped the key with a rubber mallet. It may also be useful information that I do have many other keys on my key chain, and have had this habit for years. I am trying to rule out things it might be instead of paying for things at the auto shop that might not be necessary.