They are also on non-dimmer smart switches. Yes, this is a safety feature. When traditional switches are turned off, you can safely replace a light bulb without getting shocked. Air gaps are added to dimmers and smart switches because this is no longer the case.
According to this post, even this has potential failure:
I agree with others that an air gap isn’t very useful.
In addition, I have had switches dropped from the network where cycling the circuit breaker worked when recycling the air gap did not.