I would disagree about why we have an all-volunteer army. It was the fallout of VietNam where many were drafted for an unsuccessful war and those in the know avoided the draft if they didn't want to go.
Given the climate change for equality - a continuing draft would have had to reach into all classes and the commonly used deferments and special privileged entry into the National Guard would not be allowed.
Thus, an AV army avoided sending all to war. Also, we haven't needed the massive number of troops - yet!
All males and females having a military quality weapons at home would be a nightmare to monitor. We are not as cultural coherent as Switzerland. The expense of training and controlling these guns would be horrific.
If the Martians land or climate change ends our civilization, worry about it then. The possibility of such a need for a massive armed force isn't really likely.