I wish we had a basement. I have no idea why we don't, there's no flood risk. They just don't seem to be done much in this area.
I think what it often comes down to is expense v. necessity. I would guess that frost line where you live is only a couple feet deep at worst. it's a lot cheaper to sink some pilings (of stem wall) a couple feet than to excavate and pour a true basement foundation. I grew up in new england and the front line there is down around 5 feet. once you are digging down that deep you might as well put in a full basement. Here in southern NorCal the frost line is somewhere above grade so you get a lot of slab on grade or pilings on grade as the real concerns are seismic and termites.
That totally makes sense, I hadn't considered that. Apparently here it's 12 inches. This page has a wealth of information:http://www.redmond.gov/cms/One.aspx?portalId=169&pageId=27271
Ground Snow Load 15 pounds per square foot
Wind Speed 85 miles per hour
Seismic Design Category D2
Winter Design Temo 27º F
Ice Shield Underlayment Required No
Flood Hazards FEMA Flood Hazard Map = FIRM 1999
Air Freezing Index 113
Mean Annual Temperature 52º F