Mad Max,
There are full service carriers that make money on short haul. GB Airways springs to mind and even BMI make some money. It's all about cost base. If you have high overheads then you're stuffed. Also, the likes of BA don't give a true picture because their revenue picture is so artificially skewed towards long haul. Even so, they do make money on some short haul routes.
The main difference is that the likes of EZY and FR have a control of their costs, and on the revenue side are sufficiently focused to maximise the return on sales. The likes of BA are not.