Its called a "step through" frame, and was initially intended for women wearing skirts. Notice the skirt guard in the upper-left corner of the rear wheel.
There's no connection with Asia at all, would have originally been English and European.
The curve of the top tube does allow a little more flex, damping out vibrations a bit more.
As for comfort - it really makes no difference. There's probably a fraction more side-to-side flex than a high top-tube diamond-frame, but the added damping is a positive.
Really cheap and bomb-proof are likely to entail a lot of weight by using additional metal. That alone might make for a heavy ride.