Tankengine:---- KISS method to keep it simple for low hour Pilots. 65kts full flap for a PA 28 is what the P charts say at max weight so that's the speed they were taught to fly. Yes it's a little fast by around 10 kts at light weights.
In an ideal world each landing would be checked for weight and conditions and a suitable VREF selected however that gets a little complicated for newbie Pilots.
If you need to land on a short strip in the bush then you should consult the P charts and fly the speed BUT this is not a short field landing.
Anyway....