You can’t enter into other contracts until 18 so why was marriage an exception?
The Findings section has a long, detailed list of child marriage harm. In short, preventing marriage before 18 provides for immense harm reduction in the aggregate and improved odds of life success. I’d push the age to 21 if I could. Rental car companies always had it right to restrict rentals to <25 age cohort due to frontal lobe development timeline.
(The US allows student debt and military obligations at an age when this cohort is vulnerable to systemically exploit young people, these should not be used as examples imho)
(I am also a small annual donor to the non profit performing this state by state advocacy work, no other affiliation)
Honestly, if anything the gray area should work in the other direction: no entering into life -changing legally-binding contracts until you've had the full right to vote, work, and to self determination for...oh, let's say one to two years?