Having poor website usability is like driving your car without a map through an area that you've never visited before. Unless you have an incredible aptitude for finding your way around, you're going to get lost. In addition, the more that you drive around, the more frustrated you're going to become. The possibility that you'll never want to return to that area increases significantly as the frustration is compounded. The same holds true for a website that possesses poor usability. Not only is the visitor going to have a difficult time finding their way around, but they could become extremely frustrated and never want to return to your website again. A lot of websites have great usability - why settle for one that induces headaches and forces the visitor to think too hard?