Mostly because my house was built in the 20th century. Also, at least in my area high quality cement was not available locally until the late 1930s. You can r

Mostly because my house was built in the 20th century. Also, at least in my area high quality cement was not available locally until the late 1930s. You can really see a difference in the quality of cement in the basement of houses built before vs after. Of course, wood is abundant as well.