Because HPTX boards are about common as unicorns. The odds are far greater that someone will use an ATX board with this case and our review reflects the most likely scenario. Besides, we needed to use the ATX board for thermal testing and using a larger board wouldn't have changed any impressions. Wires would've been less visible, but that doesn't change the routing issues for ATX boards. The door would've still buckled, the fan would've still eaten its filter, the fan controller and tool-less features would've still been missing, and the build quality would've still been sub-par.