I think the main reason centers around providing false information really. Speaking from experience as I've had someone close to me who's had to go through this

The process for children adopted internationally by U.S. citizens to gain U.S. citizenship differs from the regular process in several key ways. There are specific pathways and laws that govern how adopted children can automatically acquire or apply for U.S. citizenship, depending on their circumstances.

My application was denies because of lack of supporting evidence, I think I had a terrible attorney though

Fraudulent information, criminal behaviour in general