Well, by sheer statistics - many people here have been into flight sims for 20+ years (starting with the heyday of EA's "Janes" label and such). Chances are that it is now a simple peak in the age curve when so many look for new hobbies.
Could also be a result of increasingly hectic daily life - a good combat mission including planning, ingress and egress never takes me less than an hour. A bit of racing can be had in 15 minutes.
