Man we had someone in the army do this. Army doctrine is either outdated or very accessible to the poor, I don't fuckin know, but you aren't required to have a phone.
So this one weird junior Joe just decided he didn't need a phone. Got rid of it, and as a result never got the information he needed on army shit. I loved him for it, and by the law he was in the right. Can't tell him to get a phone.
Unfortunately I was his team lead, and every time my chain of command decided to put out bullshit last minute information over text I had to tell them to suck it and pvt NoPhone wouldn't be at their surprise formation.
Sometimes for important stuff I would have to drive to the barracks and knock on homies door to let him know there's surprise inspections or piss tests and shit.
The workplace should operate entirely without external communication. It worked since the dawn of man, and it should continue to work until the end of man if we want any semblance of work-life balance.
If I had to guess, the reason for the lack of a phone requirement is that, if the army required everyone to have phones, the army would need to pay for them, too. I'm sure the army loves spending money on things like that.