I do - slightly cynically - wonder if the recent move towards police forces insisting on DSC1 before granting a deer calibre might be due to some people's "good reason" being a little, shall we say, tenuous? Based more on wishful thinking than actual need? So, by asking applicants to do DSC1 what they're actually asking for a is demonstration of commitment.
If you were a landowning farmer, needing to control deer that were damaging your crops, I can assure you that, subject to the usual provisos re: criminal record etc, getting granted a FAC for a suitable rifle would be as easy as falling off a log, and I doubt there'd be any mention of DSC1.