You do see steel used in mobile towers etc because you may not be able to place an RCC structure of that height on top of a building not designed for those loads. And in single story workshops/sheds.
No, you paint them initially when you build the structure. It's quite hard to paint afterwards.
Also, if you notice closely, the steel is welded rather than bolted. Newer buildings are bolted now-a-days, which increases their useful life.
Example: https://imgur.com/a/f4z84dx
This is the current building being built that I talk about. Notice (1) the two layers of paint, and (2) bolts being used instead of welds compared to the steel structure photos in the essay
niteshpant•1mo ago
One of them: building one of the first three-story I-beam steel structures in Far West Nepal. No local expertise. No supply chain. A crew that had never done it before. We figured it out anyway.