SWBKCB - It is all a matter of timescale. ATC does not require two weeks notice that an airport is unavailable for diversions. Dynamic information is the norm. Diversions are almost always a last minute decision. Far better to have the major airport pitch in and help out with such extra traffic as it can accommodate, rather than to just shrug the shoulders and pass the buck to other agencies. If they accept half of the aircraft needing to divert, that is half the problem resolved. It really helps. Those aircraft are safely out of the system. Better to deal with the few which can't be accepted in the end than with the entire disrupted flight programme.
Ultimately, we're talking about an inter-connected system here. Flights rejected by MAN have to be vectored to other alternate airports. That is extra workload. And those aircraft will require the services of a handling agent wherever they do end up. Probably staffed by workers employed on similar T&C's to those at MAN. With all the same concerns. If the largest airport routinely shirks its share of the workload, that stresses every other agency in the system. It is not something to flaunt with a smirk and a sense of entitlement. It is the main reason that MAN has become a joke within the industry: "The airport which likes to say NO".
It's not good enough.
One final point here. Most replies have followed up on the issue of MAN refusing diversions. But my original post wasn't primarily about diversions at all. It was about the "no-can-do" culture which has become pervasive across several departments within the MAN operation. The no-divs policy is just one symptom of that. Many employees seem to brandish their bolshie 'not my problem' attitude with pride. That is a cancer on the operation, and it is a problem which has grown exponentially under Mr Cornish's leadership. Many staff don't feel valued for whatever reason, and they have withdrawn their goodwill in consequence. Some appear to take pride in being uncooperative and looking out for their own narrow interests alone. There is no team ethos. It is a major concern, and one which I would like to see Mr Cornish and Ms Smart actively address, along with partner agencies across the airport complex.