The people who know the premises day to day hold information no inspection uncovers: the caretaker knows which door gets propped open, the housing officer knows which resident hoards, the maintenance contractor knows which alarm faults keep recurring. An author who never asks them produces a tidier document and a weaker assessment. Involving them is standard method, not a courtesy.
However many people contribute, the responsible person must review the result, endorse it and fund its action plan, because the legal duty cannot be delegated along with the drafting. That review is also the quality gate: an owner who reads the assessment closely enough to challenge it usually catches the generic sections and unowned actions that sink documents, a discipline can I write my own risk assessment explores from the record side.