> But are you able to buy a decent detached house with a backyard and ...
People live in differently in different places. Many Europeans find the flimsy plywood-tyvek and fake brick houses we have in America a non-starter. And what's up with those sliding windows? Everyone knows windows should be hinged and have working shutters! :-)
I do wish I had more fixed, casement, awning, & hopper windows in the US. But supposedly the popularity of sliding windows has a lot to do with the popularity of really, really big windows, especially with large contiguous panes of glass. Horizontal sliders can accommodate the huge weight of large panes. Good luck making a sturdy casement with 1.5m x 1.5m panes of glass, double glazed.
I wince every year when it's tornado season and I see those flimsy houses being flung out by the wind. Just dig the earth, make proper foundations and build walls. It's not like you don't know how to do it, there's some fine buildings in the US (I heard).
No standard home construction even with brick - can withstand powerful tornadoes. Even if the walls withstand weaker tornadoes the roof will most likely not and it will probably result in a complete loss anyway.
You would need very thick reinforced concrete to be sure of surviving most tornadoes. And you'd have to solve the roof problem.
You are severely underestimating the power of tornadoes.
Several have been hit by tornadoes. There is even an older design (thinner with less reinforcement than modern designs) that survived an EF4 or EF5 tossing cars at it.
Regardless of the sheltering advantages of dome homes, it's misleading to say they're just as affordable. They don't resell well at all, making it an extremely risky investment. Costs of the basics (as told by the marketing documentation you sent me) can be just as cheap, until you realize you lose significant floor space and you need more materials for a similar sized home and you realize nothing standard fits. No nice doors, no normal windows. Now you need custom ones - price goes up.
Compared to the homes rebuilt after disasters, most of those are significantly cheaper to build than a dome and that's where insurance goes. People aren't willing to pay more for a non-resell-able and frankly ugly structure that isn't as practical.
Normal houses aren't purely full of standard things. People have round chair-like things, oval bassinets, exercise equipment, oval dog beds, funny-shaped cat scratch posts, round potted plants, and so on. Put this stuff beside the curved walls.
Each room in a dome home will normally have at least 2 flat walls, frequently 3. That's enough for shoving things against walls, not that you should damage your paint that way.
Usually people use normal windows and doors. You can install them the ugly way or the pretty way, and oddly there are people who choose both. The ugly way has them on bulging protrusions. The pretty way has them recessed behind openings that are often rectangles or trapezoids with rounded corners, with the space between acting as a balcony or sheltered porch.
Here is a pretty one on sale now, having gone up in value by more than a factor of 8:
