You are doubting that there are large numbers of people who use wood as a main source? Why? Perhaps you live in a city. It’s quite common in some rural areas.
I am going through the process of buying a farm property that is about 2/3 timber. The sellers heat the house completely with wood. My lender has a BIG HUGE PROBLEM with wood being the only source of heat.
I had planned that if I was going to be away that I would have a rapid deployement system to drain all the waterlines... but no... the bank is forcing me to install another system before I can close.