well as for as i understand from the translations, most of the parts used are selected for their SMD versions. and there are 2 versions of the pcb on the page though most of the parts are through hole but one of the design used 8-pin smd chip regulators and other uses 7805 in TO-92 package. Instead of putting all of the operational load on single 7805 regulator, each section of the schematics is being equipped by its own v-regulator. MC34063 is used in step down mode just to power Back light who's power consumption may reach 50mA more than all of the other circuit collectively And is for sure beyond the safe limits of TO-92 package of 7805.There could be many reasons in the mind of original designer for using Switching regulator for this particular application. switching regulator is always way better than linear ones,in this case if the circuit has to powered by internal battery in the field instead of external 12v supply there will be less conversion losses while the back light is sucking the battery out its charge very fast.