Their entire point is that publicizing their salary eliminates that privacy by telling people their income. It's a proxy measurement. Even if all they have in the house is a can of beans, publicly making more than their neighbors puts a target on them.

Because robbers tend to rob wealthy people? You get looted or shot more likely, because the robbers don't know this guy lives a humble life. They think this guy must have cash and big TV.

If my (relatively high) salary is published, they'll be able to make inferences - crucially, it doesn't matter if they are correct or not.