I guess I have a unique perspective since I have been away for a while. In the 90s I was an officer in NJ/DE region of Navy/Marine Corp MARS. We passed mars grams and ship reports, etc, and I set up and was responsible for the NJ/DE digital switch, which received and sent HF and VHF traffic unattended. Our mission was to move traffic from here to there, and we were pretty good at it.
At the beginning of the year, I joined Army MARS since I found out NAVMARCOR was no more. In the basic training manual, it states that one of the main missions of MARS is to act as a means of secure communication in the event of a DOS (Denial of Service) event. If the internet and/or email communications were lost, MARS would be able to provide a secondary means of secure communication. Digital comms are generally in a mode that is unique to the military, and messages are encrypted or in some cases double-encrypted. Passing encrypted traffic serves 2 purposes - it prevents a third party from intercepting the message, and it allows any MARS station to pass classified information without a military clearance (providing it is encrypted with a key that is not known by the station). To me, that's a pretty important mission. With all of the hacking in the news these days, MARS can be called into action at any time for no apparent reason in order to pass secure information between government agencies and the military. MARSGRAMS are a thing of the past, but that doesn't mean MARS is obsolete. It's a different world, and MARS has a new goal.