Because historically, owning a house has been very affordable and lumber is abundant because the landscape was not denuded for firewood over the course of millennia.

Lumber is not timber. Lumber can be moved about by a single pair of hands and fastened with nails...American construction takes advantage of the industrial revolution and uses commodity nails.

Worth noting that where Americans use concrete and brick, they also use steel reinforcing so that their buildings don't collapse brittle collapse from earthquakes and wind.

Why do you think that would solve the problem?

Keep in mind stucco is very common in Southern California. Basically a 7/8” thick layer of concrete on all the exterior walls. It is fire resistant. Many such buildings burned down.

This isn’t the three little pigs where the brick house is the solution. And that wasn’t the moral of the story anyway.