Unlike a lot of 'neutral' correspondents on here, I do like MAN a lot. But my only criticism would be how long it sometimes takes the airbridges to be put in place. Over the past five years, I'd sat there was at least a 5-10 minute delay on about 15% of the flights I arrived on.
Perhaps bad luck and purely subjective I know (and a lot less inconvenient than having to embark/debark onto a bus - that's only happened once) but I think this is one area MAN could improve; so I could see why locos with 25 mins turnaround would be reluctant to use them (do they pay less also?) if there is a reliability question.