Metal and cotton are different materials with different properties. Cotton doesn't rust easily. Iron doesn't get tie-dyed easily.

Third option (ignoring your disputable conclusions of vandalism): it does wash away and you just don't 'get it'.

Even if it was permanent (it isnt). Why would painting dirty/rusty/messed up stuff with a coat of black ink be "defacing our landscape"? If anything the black ink would cover up the dirt, rust, blemishes, etc with an even coating of black. To my eyes this would be much better looking than disabused and dirty.

people stand on it, and probably spit, animals pee or poo on it, some paint wouldn't damage it, it would probably protect it. You are so negative, cheer up.

It doesn't wash away. They use some expensive paint for the purpose. It takes a while to dry.

And it's not defacing anything that could be defaced, it's mostly steel that hundreds of people step on every day.

"eco-friendly water-based paint"