Those are addressed to a court or government agency in a specific place. The advice offered isn't for a bunch of rando people on the internet across all number

Those are addressed to a court or government agency in a specific place. The advice offered isn't for a bunch of rando people on the internet across all number of jurisdictions. And it is only general advice about an area of law, normally at the appellate level, not specific fact-dependent advice to a real flesh-and-blood person. Amicus is also normally an opinion to sway the court on broad policy, not a determination of facts in a specific case.