Informally, it's put forward as one of the most successful government programs in history: it succeeds at all it's objective, comes in at or under budget, employs few people, and avoids the scope creep that kills other successful programs.
It's only shortcoming: it doesn't actually do anything.
Nobody wants to be the guy who got the nation caught with its pants down if conscription needs to come back in a hurry. The same reason the military budget always ratchets upwards.
Measured as a percentage of GDP (which I'd say is the most sensible way to measure it) the US's current military budget is lower than at any point since WWII aside from a few years between the end of the Cold War and 9/11.
Struggling to see the relevance, but, thank you for teaching me this:
The U.S. Army is the permanent, professional standing land force (Regular Army, Reserves, National Guard),
while the Army of the United States (AUS) was a temporary, authorized component used primarily during major wars to rapidly expand forces through draftees and volunteers.
Under U.S. federal law, men ages 18–25 must register with the Selective Service System to be eligible for most federal jobs. Federal agencies enforce this under hiring rules in 5 U.S.C. § 3328.
The wording is a bit strange - technically all men (18-25) must register. When I tried to register, I was told I couldn't because I was already registered.
The Selective Service auto-registers people from various data sources.
But this puts me in a weird spot: I've never actually registered. I am registered. But I did not register - which is the requirement.
There are Kafka-esque parts of the US government where this distinction could matter.