let's say you bleach down a perfectly smooth countertop in your kitchen. okay, it's clean, there's no bacteria there. for about two seconds. probably less, in reality. we can't see microorganisms with our naked eyes, but they are as much a part of our physical environment as the air.
put differently, you can't make them go away by cleaning compulsively. not even for a moment. not in your home, at least. sure, if you see mold growing on food, throw it out. but you aren't about to out-clean nature's ability to survive.
remember, nature has been playing the game of "gotta inhabit every potential niche, ESPECIALLY if nobody else is there, because then there will be more room for me!" for a few billion years. a lifetime spent applying cleaning products isn't about to make any headway, nor will it prevent disease beyond a certain minimal level.