Whilst the new security screening equipment may not be needed, I think you will find that passengers will prefer to take as much carry on baggage as they can, and when they realise that the airport down the road (BHX vs EMA or MAN vs LPL) allows them that facility some will vote with their feet.
I agree there are a number of dodgy scams, such as EMA's car parking that can help to make up for money the airports don't make from the airlines, again, passengers and also their friends and relative who get ripped off by the EMA shortstay car parking charges will ultimately make their decision - a slightly higher fare, versus extra costs for car parks, food, and more creature comforts. Not everyone is a cheap skate.
You can't treat passengers like sh*t for ever and not expect to lose a few.