Because a contractor has way less paperwork than I have to deal with for each employee - at least in my country. We're also free to set our own terms instead of the lawfully required ones, and generally, contractors in IT want that. I'm even doing the contractor paperwork for some of my contractors as it's very easy - I can basically generate it automatically; definitely not the case with employees. An employee also costs way more money (that goes to the government).
> Do you also pay your employees to wash the windows, and vaccum the office
Irrelevant argumentative foul. No paperwork is eliminated doing that and no other advantage is gained doing that, so of course I'm not doing it.