According to TFA, camera raw isn't required to use "Super Resolution", but regardless the answer to your question is "people who cropped their original photo".
I can’t get the Enhance feature to work without using the Camera Raw plugin, but yes it does work for ordinary jpegs and such. You have to open the file through Bridge. If you open Camera Raw through Photoshop (in the Filters menu) then the Enhance option doesn’t show up :P
I had a bunch of 25-year-old photos I wanted to print! At that res the enhancement really helps.