You see, that statement there is simply not true. I would love to see a slider to turn off digging zombies. But I dont avoid zombies and never have.
How about the FACT that a lot of people enjoy carving out a piece of earth and making a base out of it. For me, thats what it comes down to. I have always loved making a beautiful storage base underground. But I have never ever avoided zombies and have always had a sniping tower above ground to face them.
It is obvious from your statement that making an underground base is not your playstyle. There are a HUGE number of people out there who love to play this way, and why shouldnt they. They are not affecting you in any way at all. AND they are having fun, which is why we play games.