If you didn't assign a FOID card to EVERY citizen, regardless of gun ownership, then groups such as the NRA would accuse you of trying to create a gun owners only registration.
By including everyone in a national FOID card system that argument falls flat.
I would argue that a national FOID card would be much more cost effective and efficient than the current background check system.
In addition, it would offer a way for private sellers on websites such as Armslist to also easily verify the legal eligibility of a potential buyer.
Why We Assign Social Security Numbers at Birth: https://money.usnews.com/money/blogs/planning-to-retire/2011/05/06/why-we-assign-social-security-numbers-at-birth
"...to claim your child as a dependent on your income tax return, open a bank account or buy savings bonds in their name, obtain...
Ugh... Please take literally 1 minute to actually read the source article.
The point of EVERYONE being assigned a FOID card is so that everyone would be considered a gun owner, even if they weren't.
In other words, it eliminates the gun owners registry excuse because everyone is included in it...
If you read the entire source article above it explains the reasoning by comparing it to the issuing of Social Security cards which are commonly applied for by parents at birth.
Thoughts and opinions...
Is it time for a National Firearm Owner's Identification (FOID) Card: National Firearm Owner's Identification (FOID) Card
"To achieve this uniformity in American gun laws we would like to propose the idea of a National Firearm Owner's Identification (FOID) card system...