On a working site, the crib room and the toilets are where your people take their breaks. If they're grimy, cramped or out of soap, morale drops quickly and the complaints land on the ops manager's desk, not the cleaner's.
Industrial sites are also harder to clean than offices. There are shift changes, forklifts, loading docks, exclusion zones and site rules that a general contractor often doesn't understand. Cleaners who turn up without an induction or the right PPE create a safety risk, and the ones who avoid the floor entirely leave dust and debris building up on walkways.
For site and operations managers, that means supervising a contractor on top of running the site. You need a team that knows the rules and gets on with it.