See the "roads, bridges, dams, and levees that are falling apart from age" sentence in the previous section. As you can imagine, the longer these structures are in operation, the more their condition deteriorates. Whether repairs and upgrades will be enough, or whether someone must bite the bullet and find the dollars for these expensive new projects, the civil engineers must help plan each project and oversee the construction. There's the beauty of it all.
Of course, if you're really lucky, you might hang around long enough to see a building that's too far gone to be propped up any longer. At that point, you get a front-row seat for a controlled demolition event. That alone is worth all those years of engineering school.