I know i have'nt got the answer to the reason why Midland Centre trials are so poorly attended lateley, but i offer you my opinion anyway. I think that people have become far more choosey about when and where they ride, for a number of different reasons - be they family, work commitments, the cost of getting to/from and entering events, event dates clashing, and even the choice of venue can be a sticking point for some i'm sure.
Take your trial at Shatterford for example; it was run on a Saturday, with another Midland Centre trial (road-based), being run on the Sunday. Now I appreciate that you cannot always avoid clashes, but it has to be said (speaking as a rider who preferred to ride the Kings Norton trial on the Sunday), my first thought when i saw the date clash was - that's a shame, i would have gone to the Stourbridge trial, had it not been the day before another Centre level trial. My reasons for this was primarily work commitment Saturday morning, and family commitments requiring me to be at home at least part of the weekend (in this case Saturday afternoon). Also it has to be said, that a few people feel that Shatterford, as a venue, has become over-used, and can be difficult to ride in wet conditions.
With all that said, I myself rode last Sunday at the Kings Norton road trial, and was more than disappointed to see an entry of only 24 I think. This trial normally stands out as a great trial, and to see so few competitors is very demoralising, especially for the organisers i'm sure, who have to put no less effort into organising a trial of this size, no matter what size the entry. I have no idea what kept the majority away, except for maybe another event (Sammy Miller Round at Devon) which may have tempted some away, the only other thing to my mind is the cost, mainly in registering and insuring a bike for the road.
Whatever the reasons may be, I for one hate to see the decline of numbers, because the more trials that get run at a financial loss, will surely see more clubs refusing to take the gamble, which can only lead to fewer trials. In which case we all lose out!!
I for one, am always grateful to clubs/organisers/observers etc for taking the time out of their own busy lives to make it possible for the rest of us to participate in the sport we love - basically without them, we would have no trials to speak of. So, before its too late, why not have more communication between clubs, regarding dates/venues etc. so as to avoid costly clashes for both parties, and also anyone who knows someone who has a bike but can't be bothered cos he ain't got a van, offer them a lift, and share the costs a bit!! It still has to be the cheapest form of motorsport available at around £15 per event!!
We all need to make more effort - or we will all lose out!