Probably for most of us this occurs only when we pedal. I took an old chainring off a bike because I was considering putting it on another bike so that I could change the gear ratios. When I looked at the Aluminum chainring I noticed that the teeth were worn on sections and that on other sections the teeth looked like they were almost new. This uneven wear was probably caused by mashing as opposed to spinning. Any way it would appear that rotating the crank arms 90 degrees maybe each time we replace our chains might even the wear out on the rings. I know most people just buy a new bike when the chain needs to be replaced.