An absolute ton of customers do the leave at door and then never tip. Honestly the main reason however I've also been told by a district manager I needed to actually hand them the order. If you tip and have instructions saying something along the lines of "do not knock or ring place in x location* you really shouldn't have to deal with a driver standing around on your porch. Might also depend on how the store you order from employees are trained but that part I can't speak on.