What those reports do is let your local admin and mods know about potential problem users or instances, and gives the hosting instance a chance to address the conduct of their users. As an admin I can see a total of reports for an instance and a lot of reports is a good indication to silance or defederate.
For example, I can see that this particular instance follows two of our accounts, no one follows them back, and they have had two reports for content submitted against them. This starts to give me some insight as to if I need to silance or suspended the whole instance and what that impact to my local users would be. In this case, absolutely zero impact aside from keeping some reportable content out of the Federation feed 👍