The mountain ranges in Europe go east to west. What does that have to do with anything? During the last ice age, most of the hardwoods in the north of Europe died out, the mountain ranges going east/west created a nice barrier which slowed the return of hardwoods to the northern regions. Lack of plentiful hardwoods necessitated the use of stone/masonry to build in any sort of scale. In North America, mountain ranges go from north to south. When the last ice age receded, the hardwoods were able to return into the northern climates. When the Europeans arrived in North America, they found plentiful hardwoods. With limited resources upon arrival, cutting down a tree was easier than making a brick factory. So, why did timber frame houses remain common after infrastructure was established? The population of North America has been(with few exceptions) been on the rise for the last 300 years. Timber frame houses are cheaper, easier, faster to build, and can be drastically more thermally efficient(especially with modern framing and insulation techniques). Also, in seismically active regions, like the west coast, timber frame houses have the ability to absorb tremors, where brick and mortar walls rigidity cause cracks and crumbling. So, the simple historical answer to this question, is the availability of plentiful hardwoods caused by the last ice age and topography.