An excellent point. Most modern germ theory says all bacteria is bad. This, despite the fact that our guts are full of bacteria and that you simply cannot avoid ingesting bacteria. Nevermind that plenty of wood cutting boards are full of beneficial bacteria that keeps listeria and e. coli at bay.

Edit: Also there are literally some forms of cheese that you cannot make in sanitized stainless steel. The combination of bacteria you need needs to be impregnated in the wood.