"Pure theory" or Hayek / neoliberal theories don't seem to be just about perfect S/D curves and reasoning with S/D curves doesn't prove anything, it's just a vi

"Pure theory" or Hayek / neoliberal theories don't seem to be just about perfect S/D curves and reasoning with S/D curves doesn't prove anything, it's just a visualization tool. I didn't understand why the curves are reversed ?