Actually it is.
Many of these ships can provide power (electricity), water (desalination), the Marines can help provide security (a major concern after such events), command and control and communications. They can also provide some logistics: helicopters etc.
Many of your civilian helpers actually STRESS the local logistics even more (they are not self contained).
The military is able to operate in the most austere and even high threat environments (example Somalia) where civilian aid organizations can’t even get to.
This has been done many times and works extremely well: https://en.wikipedia.org/wiki/Operation_Unified_Assistance
But it never fails, people criticize it.
I was in jest. The Corp of Engineers works miracles. I have numerous FMs which describe civilian support operations, including water supply and sewage treatment. Army portable medical facilities are better than many permanent facilities.