I think that people are just bored a bit with Box , As a squad we have been flying the SIM for over 20 years together and box does not have as many planes or theatres as the old il2 so lacks a bit of variety, the only good turnouts are for special events now
DCS is the new shiny toy and interesting as it throws up new challenges but unless we get start having coop type missions then I can't see it being a long term solution. There is already a disparity on who has a particular plane and map so some communality will need to be agreed and I'm not sure some folk will want the expense of that just to keep flying.
Having said that I will still attend both SIM nights as much as possible