Generally people don't commit to a campaign if it's not something they want to do. In my experience, the "scheduling conflicts" referred to are probably other responsibilities outside player control. I can't claim to be intimately familiar with military life, but I presume they aren't being ordered to supercede the players' will to be there, but to take advantage of the military hierarchy to clear their play time from other orders.

I play with the person who makes my schedule, and it's awesome.