I joined AF MARS back in the 90's and was issued the training calsign of AFT2PH -- but I never finished my training due to immediate family duties (and my job). With very little 'off-time' for the hobby of radio, I dropped MARS. I have always regretted that move, and resented my responsibilities at the time because of my choice somewhat. When I retire for good, good Lord willing, I will surely 're-up'. As for it's role in actual military communications,the redundancy of internal com services, coupled with today's com technologies outside of it, MARS may be less relevant these days, sure...
But how many actual combatants can we afford to re-direct to the respective comm branches of the services in the event of a world war, or global natural disaster?in this age of mass-destruction capabilities by rouge countries, how can a 60 year-old HAM contribute to the efforts of his nation's defense and survival, or that of his own community?
Whether or not those operators now enlisted into the service are EVER activated, in my humble opinion, it's an irrelevant debate. Totally moot. I strongly believe that another Carrington Event is inevitable, and in such an event, there will be no civilization, and likely, no MARS service anyhow. But the TRAINING they gave me!! Whether or not I live long enough to witness the total breakdown of civilization, I consider that training as a priceless asset to my preparedness. So is my NTS (National Traffic System) training and periodic usage. The two formats used are stunningly similar. That is because they contain 'error-correction' protocol. Just imagine the benefits of that if/when the grid goes down! What offers error-free (or at least,low instances of errors) in communication when nobody has a computer to do it for them?
Massive EMP prep or not, I urge everyone; If you have the time and inclination to serve, to serve. At minimum, check into your local NTS NET, if there is one, and learn basic traffic handling format. It may save somebody's life in grubby times, and boss/commander may even keep you "gainfully-employed" to maintain communications -- even if you're 90.