Because a small company has the ability to supply cleaning to X square metres across one city.
A middle-man can say "We will supply your cleaning in several cities no matter your office size."
So a company pays a higher cost - but only has to deal with one contract, which saves them effort elsewhere.
It's the same as taxi companies. It would be cheaper for you to call a small firm with lower overheads, but you're happy to pay a premium for convenience.
A middle-man can say "We will supply your cleaning in several cities no matter your office size."
So a company pays a higher cost - but only has to deal with one contract, which saves them effort elsewhere.
It's the same as taxi companies. It would be cheaper for you to call a small firm with lower overheads, but you're happy to pay a premium for convenience.