That's true, and I've said as much several times.
However, a premium ceramic coating such as one based on silicon carbide does considerably more than just facilitate washing and drying. It adds UV protection; increases resistance to chemical damage from bugs, bird droppings, tree sap, etc.; enhances protection from light scratching, such as swirls from improper washing; and provides durable water beading which means you never have to wax the car.
To get the additional rock chip protection that PPF provides you take on the risks of edge lifting, dirt lines at the seams, yellowing with some films, and loss of ability to touch up small chips.
I'm not saying there is not a good case for using a PPF. I'm just saying that, as with almost everything about a car, there are some trade-offs involved.