I too am glad to hear you and your wife are o.k.
I grew up in Ohio in tornado alley and recall seeing a few twisters too close for comfort.
The oddest incident happened when I was stationed In Tucson in the Air Force. My crew and I were load training in a hangar, when suddenly the wind kicked up, lifting a 4 foot square aluminum drip pan from under the plane, hitting me and my crew chief before flying out the hangar door. We closed the hangar door, paused our training. The lights went out briefly, then the phone rang. The control tower was calling to check in on us, as a tornado had touched down about a thousand yards from the hangar!!
I had mentioned to my guys that the sky had that peculiar tornado look right before we started training, they didn't believe me. (They weren't from tornado-prone hometowns.)
After that, they listened very seriously if I expressed any doubts about the weather.
Then there was the time we almost got a direct hit from lightning during aircraft recovery....but that's another thread.
I think IMHO the timber is simply the preferred method...brick homes would need more skilled labor that wood frame I'd guess. 'Tis all about the buck...
And I don't know of any areas that mandate a shelter/bunker. Heck, in the house I grew up in we did have a basement, but the last house I lived in there for about 6 years, all we had was a very damp crawlspace.
Not much protection there I would imagine.