The word disgusting is often used to describe drop off charges and is often a hot topic on the airport's facebook page. If the charge was hidden in the price of the airline ticket no one would say a word.
Passenger expectations is that airports should be charities and charge for nothing.
If an airport is dominated by players such as Ryanair and Easyjet who don't believe that an airline should pay for services they get from the airport operator, then someone else has to. That someone else is the passenger.
So as you say, either the air fare goes up, people wind up paying for drop off, trolleys, fast lane security, or any other wheezes that the airport can dream up to replace revenue they are not getting from the airline customers.
This I think is why a domination of low cost (no frills - call them what you will) airlines is not necessarily a good thing for the passenger experience.