I don't really see the big deal. Ford always had something like the ST-line in Europe, either it was the Zetec-S or ST-Line. In the US, there were a few different appearance packages for the regular Fiesta. They had ST skirts, ST spoiler, chin spoiler, and a different rear diffuser. I have never seen one on the streets, but they were on display at auto shows. Ford also did the same thing with the Focus Mk1's. There was the SAP, Street Appearance Package, that had a spoiler, skirts, different bumpers, and different wheels. Very few of these cars had any performance upgrades.
For the most part, people would rather have the looks rather than the performance. So many complaints about harsh ride, poor MPG, need for premium fuel, uncomfortable seats, lack of an automatic, and torque steer. These people should never even consider a ST, but they do and they complain. Ford just responds to the market by giving people the look of performance without having to give any performance. It is no different than any SUV. People want the look that they could go off-road without actually going off-road or dealing with the compromises that come from driving an off-road vehicle on the road. People just want the image.