It's national park service, so it might be a more remote bathroom. In an office, toilet paper needs to be replaced daily. In a park, I'm guessing you would only need to replace weekly or monthly depending what's going on. If there are a ton of people at that camp sight, the toilet paper might deplete much faster than if there weren't many people. So rather than checking every day to see if there is toilet paper, this seems totally reasonable. Anyway, I'd much rather have the warning than not.