JohnR, OTOH - If you would receive some service someday above and beyond the call of duty from ATC, for instance in an emergency, are you willing to pay more? Or would you be willing to pay a fixed amount for each radio call? Or do you think the ATC guys will want to have their salaries based on the amount of service they provide to all aircraft combined on any given night? Slow night - less pay, busy night - more pay?
The truth is that the costs that ATC makes are mostly fixed. They need to find a way to transfer this more or less equally and fairly over all the aircraft that make use of their services. So they need to convert fixed cost into variable billing. Preferably in such a way that the process of calculating each bill is fairly easy and thus cheap. Flight plan data, including the route and rules you fly under, and aircraft data such as MTOW is already in the Eurocontrol computers. Easy to generate a bill. If controllers would have to tally the amount of service they have supplied to each flight (and how do you tally service anyway? By seconds of radio comms? By radio calls? By sectors?) the system would become horribly complicated and thus just calculating the invoice would become very costly.
Any system where fixed cost are converted into variable billing will have winners and losers. But if you want to eliminate that by making the system more complicated, it gets more costly overall and everybody loses.