A ramification of so many season ticket holders not turning up so frequently more than anything I suspect. I missed 4 home league games myself this season but my ticket was always used. The apathy of a few thousand costing everyone else.
I realise the Cardiff game was rearranged at short notice which contributed to the lower crowd, but I was recently informed there were 15k unused tickets for that game.
Everyone has things going on in their life, but if thousands can't (or won't) attend half of the games you shouldn't have a season ticket.