The first post and title of the thread is a gross generalization that I would not follow. Yes, the majority of students don’t need anything in their Additional Information section. For example, don’t insert an extra essay.
But there are some instances that call for using this section.
I’m a college counselor. I’ve had students use it to share why they are an early graduate, why they took a Gap Year and how they spent it, sharing about a learning disability, explaining extenuating circumstance that affected an uneven academic record, significant life events such as illness (perhaps taking them out of school), death of a parent, having to work to support the family, natural disaster, etc. They may wish to share an abstract of a research project. There are certain instances where using this section is appropriate, but for most, they won’t need to use this section. I would never generalize that nobody should use this section. It is there for certain reasons, such as some examples I gave.