We have no polishing system on our boat and have never had any water, dirt, growth, etc. in our fuel. None of the people we know and boat with have fuel polishing systems and none of them have had any problems with fuel, either. If a boat needs to have a polishing system run on a regular basis to prevent growth in the fuel I would suspect a problem with the boat's fuel system.
Or the fuel source.
Like you, I have never had water, dirt, growth, etc. in my fuel. I keep the tanks topped off to minimize condensation and I add a treatment that's supposed to take care of water and any growth.