These sites are large, often remote, and they run when conditions are hard on people and equipment. Coverage has to reach yards, perimeters, and restricted areas, including when visibility is poor.
The right people need to move through gates and zones; everyone else should not. Interiors are often difficult to rewire, and safety rules are as much a part of access as security.
For construction sites, remote yards, and warehouses in different places. Check them from the office, with no server to keep up at each site and updates that happen on their own.
For plants, refineries, and large warehouses. Appearance Search finds a person, vehicle, or truck type across your cameras from a description, which is how an incident review actually starts.