When I stop at a gas station, there are as many as 20 pumps and each pump may have up to 4 stickers on it.
These stickers are replaced periodically whenever an inspection of the pumps is done to verify that the pump is operating properly.
These tags are not permanent parts of the pump but just a tag to show that someone checked the pump on a particular date.
There are 1000s if not 10000s of gas pumps in states like California, Texas, etc. and if I remove "one" sticker per state as a rememberance of my cross country trip - I don't think this is a major issue.
JMHO
Take care,
Jerry