[trprog]

>So a company pays a higher cost - but only has to deal with one contract, which saves them effort elsewhere.

They have fewer contracts at any given time but also the contracts can last longer.

If I directly hire people to clean an office, when they don't want to do it anymore I need to find other people to do it. Selecting people, negotiating, getting payments set up with accounting etc. Its a distraction from more important stuff so I want to do this as rarely as possible.

If I hire a company/agency/middleman they can replace people without me having to even be aware its happening. At the point "keep the office clean" is essentially solved. Its possible I will never need to think about office cleaning ever again and I can get on with running my business.