This reminds me of some family members that lived on a boat. As soon as they finished maintaining one thing (e.g. painting), they could immediately start over again. It was an endless cycle of doing maintenance to the boat. They really wanted to live on a boat. Eventually they sold it and bought something else, though unsure if the maintenance was the cause.

From an operations viewpoint, it’s easier to pick a degree of parallelism that makes this a continuous operation.

You don’t have to close down and start up maintenance work, you don’t have to scale up and down the number of workers, etc.

(On farms, there’s an opposite force at work. Farming itself is highly cyclical (not much to do in winter, relatively), so maintenance was done cyclically, too)

I don't know about your jurisdiction but every bridge in my area gets inspected by qualified bridge inspector at least every 3 years, and if there are potential issues more often.

>Of course, bridges are not normally sitting in salt water

Again, not sure about your jurisdiction, but many jurisdictions use chlorides for winter ice melting.