Tragedy of the commons doesn't apply because clearly it has not and will not become a problem, so clearly this is NOT something that is being exploited.
You fail to understand the theory. The whole point is that it's not a problem for one person or a few people to do it, but is a problem for everybody to do it. Therefore, it's fundamentally unfair (and rude) for you to do it because everybody can't. That's why the theory refers to such people as a "freeloaders."
Not to mention the fact that to use the phrase in such a petty and ultimately insignificant situation diminishes it in cases where it actually applies. Much as referring to Hitler in an argument diminishes the evil the man actually committed.
It's a theory of consumption and resource management. It applies whether or not you think the resource is insignificant. That's like saying 2+2 doesn't equal 4 because "those numbers are too small for a concept as important as math!"
...and I might add that while you may find courtesy and respect to the rights of others in everyday transactions such as waiting in line to be "petty" and "insignificant," many don't, which is why they get so riled up over this issue. They take those concepts very seriously.