Some dealers edit the chassis number and other relevant info on the auction sheet of a higher grade car with same colour and model and show that fake auction sheet to the customer(according to what I've heard). Other reason is ignorance on the side of customer, no dealer in market told me about the grade etc of the vehicle, when I was looking for Aqua, until and unless I asked them myself. Then they told "sir isski diggi replaced hai, R grade hai" etc etc. So if customer is not aware about auction sheets, they won't ask for them and according to my personal experience, dealers didn't mention anything about grades themselves.