the staff handling the car returns are given targets to spot a certain amount of damage.
I have collected cars at some small outlets where i've been waiting to be served and seen the previous renter arrive and drop off the keys - so there was zero chance of any inspection.
Taking photos has not always helped me, hertz told me I signed the contract and charged me regardless. In fact i had the same car for two rentals with a few days gap between and recognized the damage from the first rental (where it was not recorded at the start and I wasn't charged when I returned it the first time). When I returned the car the second time I was charged even though I recognized the damage from the first time I rented the car. The difference was WHERE i returned the car - the second location probably had people more concerned about reaching their damage inspection target.
I don't rent from Hertz anymore.