On flat land, basements are a function of home (and land) price. In places where the frost line is not very deep, a basement is a luxury. One of the most expensive parts of the house is laying the foundation, and not building a basement is far cheaper than building a basement.

If the frost line is lower, then a basement is very little extra cost since you are digging deeper and laying more concrete anyway.

If you are building on a hill, then making a 3 story house is also very little extra cost.