Worth remembering chaps that recently the PFA/AOPA have asked VFR pilots to report to them when Class D transits are denied. If I recall correctly, this is because when Class D airspace allocation is granted, it's usually promised that the effect on GA will be minimal.
Apparantly, if a transit is refused, the PFA/AOPA get involved, the controller has to write a report, which eventually should mean that it's easier for them to provide a clearance rather than bluntly deny one due to the paperwork.