Wild speculation here obviously, but it could be a regulation play--there's a lot of potential legislation that would regulate what you can legally 3D print, which would warrant a system to be the age-verification equivalent for 3D printing.

If this is the angle then I'm even more suspicious that they're secretly pushing for the legislation so when it goes into effect they'll effectively be the only game in town.

This is admittedly a bit tinfoil hat, but they wouldn't be the first company to attempt to legislate away the competition.