I would say I disagree about it not being cultural thing but as you pointed out I have not flown Knights or Bishops so I can't really tell. I do know from chatting with squads that fly Knights and Bishops that each country does have its own culture which is to some extent different from each other.
The Rooks have worked very hard at changing our culture and developing inter-squad relations, operations, and reliability, looking at everyone as countryman and helping them out. Various levels of success. But it did help dig us back out of the bucket that we were in for a very long time.
But I don't know if a cultural thing with Knights so can't really comment or offer suggestions or even saying what we did would help you or not.
Knight numbers have dropped but basically only in the last two month drastically. Right now they seem to be at parity level with the Rooks or just below with Rooks still building strength while the Knights are losing numbers. Bishops still have a large pilot base.
This is an excel file I started tracking a while back that several squad leaders and I have talked about when Rooks were experiencing severe number problems. Its interesting and will be interesting to see if this is momentary glitch for the Knights or a start of a longer trend. Basically before now its has been the Bishops with the most pilots, then Knights, and Rooks with the least.
http://www.dgideon.org/countries.xls