I avoid departing MAN if at all possible, the security procedures are literally the worst of any airport I have travelled through in my years and while I don't keep an exact count as a BA LTG and a DL 2 Million Miler I've been through a few :-) They have just replaced the CEO at MAG but its been terrible for years, so doubt anything will change. Ultimately its not hard to manage the security and screening process, there's plenty of airports that do it well so they can learn from them pretty easily.
I guess when there is essentially very few convenient alternatives for passengers most will put up with the poor experience and when there is no incentive or real accountability for the airport to improve they will continue to deliver a poor experience.