If EC isn't monitoring the situation like that, more fool them. Think how much money Tesco has made, partly down to its Clubcard system that allowed the company to keep tabs on customers (not in a sinister way, as I doubt they really care about me as a person) and tailor offers for individuals.
Tesco also gets to see when I don't shop there for a while, hence me getting special offers to entice me more often than normal (we rarely shop at Tesco now, bar petrol occasionally).
Now, obviously they can't monitor people who by something in Tesco without a clubcard, or buy a train ticket without being logged in, but if EC had any sort of reward system for people who booked through their site, more people would login and the benefit would be the ability to see if people did suddenly stop buying tickets. Or, if they changed to buying different tickets.
From what people have been describing on here, EC may as well operate more like an airline and just have two choices - meat or vegetarian - and then go down asking people what they want. No choice, take it or leave it. Far easier than taking orders and coming back.
The problem with a train is that the exact passenger numbers may not be known before departure (given those boarding with an open/walk-on ticket and no reservation) and people come and go. This is something that is made far easier for the crew on a plane, or indeed Eurostar.