I thought that was weird also until I became a homeowner (in Seattle). There are two other townhomes in my cluster, both are owned but unoccupied most of the time. My neighbors have other homes, one is technically owned by parents in China (who might occupy it someday, my wife is Chinese so chatted about it with the person who occupies it occasionally). It might be totally weird luck, but maybe those houses are being bought by a small segment who are acquiring multiple ones?