The minimum is set to keep in check those who do not have the initiative to go further. Also, one item that I have considered in the past is the identification caps that are used. Most often these are the plastic ones that slip over the top of the rebar. I have seen way to many of these pounded into oblivion so that the intent of identifying the responsible party is useless.
Some animals nibble the tops off.
I have been digging and popped them off the top.