> passage ways: doors, handles, stairs handrails, subway grab bars... All the things that propagate infections in very dense populated areas

Sterilizing those often increases disease spread. By default, they are covered with a microbial community that can outcompete things that are human pathogens.

If you sterilize it, then you’re either leaving a coating of food (mostly dead skin cells) for pathogens to eat, or a coating of nasty poisons that strip the protective barrier off people’s skins, which undermines their ability to fight off what pathogens they do end up touching.