Why the distinction reaches your premises
The arrangement determines which policies respond if somebody is injured at your site, who has the authority to direct how work is performed, and how quickly a replacement can be assigned. It also affects continuity, since an independent contractor may service several clients directly and prioritise accordingly. None of this makes one model better, but it does mean you should know which one applies before an incident rather than during one.
It also affects your own obligations in some settings. Buildings with contractor compliance systems generally require evidence for everybody attending, and that evidence differs depending on the arrangement. Where your premises has induction or screening requirements, knowing who is engaged by whom determines who is responsible for making sure each attendee has met them before their first shift before somebody arrives who has not completed them.
