MV - it is because they have a shortage of pilots. To help alleviate the problem various measures are being taken. One of them is the cancellation of some flights. The ones picked are ones where the passengers have an alternative airline on the route, such as BRS to EDI/GLA. This is "less worse" than cancelling flights on routes where EZY is the only operator.
It is a shambolic state of affairs that I, and my colleagues, feel most embarassed about. I offer you my apologies for what it is worth.
Cheers
WWW