While there is certainly some tendency among the travelling public to imagine dark conspiracies, the fact is that these type of situations do raise difficult questions. As has been discussed here before, where exactly does an "unavoidable" delay start and finish? If flight 123 from A to B is cancelled or delayed due to, say, weather at B and then the airline responds by rearranging aircraft and/or crew so that a completely unrelated flight 456 from X to Y is cancelled, is this due to weather? Or is it a commercial/logistical decision at the discretion of the airline?
More generally, where an airline must cancel a certain proportion of flights (say due to fog at LHR), the choice of flights to cancel is made on commercial and logistical grounds. As far as an individual pax is concerned, the airline may be forced to cancel some flights, but is not forced to cancel his/her particular flight. So what does this mean for denied boarding compensation, etc?