You apparently don't realize how advanced robotics and artificial intelligence have become in the last few years. Yes indeed, systems can, will, and are right now as I'm writing this, being developed to do EVERYTHING a human laborer does. I agree with you, all of the systems and infrastructure aren't in place in 2024, but in 2030, or 2035, forget it. Intelligent, autonomous robots will do EVERYTHING you are doing now as a janitor. New construction (including old buildings) and building codes will be compatible with this technology, allowing robots to do everything (including mopping stairs and everything else you mentioned).