Most of the time, the world changes in such a subtle, gradual way that it's hard to notice. For instance, we don't usually notice people aging until we see an old photo that shows what they used to look like or we go a long time without seeing them.
The same thing goes for those ordinary things we use every day. Although it's difficult to notice, even the smallest ways that we interact with things do have an effect on them.
And when those things are open to the public or the elements, we're actually have a chance to see those effects without waiting a lifetime.