Because wood is a natural material, and living in it or with it is healthy and pleasant. The wood cellular structure functions as an extremely good natural insulation; the material breathes and balances humidity. In addition to all good characteristics, wood is the most pleasant construction material from the psychological aspect.
Environmental protection arguments also speak in favour of the use of wood. Wood is a renewable raw material, completely neutral from the aspect of greenhouse gases. Its procession and treatment produce no harmful emissions, and special raw materials or high energy consumption are not necessary.