So yes, the pilot can screw up. This is especially bad when it is one of those guys who will never admit an error and views the skydivers as low life cattle he is forced to fly until his airline job comes along. Some of them just don t care if you land out. However, a conscientious dz operator will get rid of these guys right away. If your customers land out, not only are they at a higher risk for injury, they aren t buying jump tickets if they are busy walking back or picking their canopy out of a bush.
Good pilots are really into spotting and take a lot of pride in it.
We have had some land free bags and cut away trash right in the landing area - more than once. Sky gods who think they must have final authority over everything, including the spot. These are the people who insist on looking out the door for a good long time, with the result that their group opens right over the dz and everyone else is long or the plane goes around. The first group always should just barely make it back in from a short spot. You almost never see people land short, while landing long is very common.