In my former role as a CFO, I was shocked to find out that our IT Services provider regularly took kickbacks when they referred us to technology providers. Yes, I understood they made a commission when selling hardware and software. But the kickbacks were, and still are, something quite different.
Many IT Services companies get (rather large) kickbacks when they convince you to use an email provider, an internet service provider, or other technology provider. And this is all without your knowledge. Because of this kickback, you have to wonder if they helped you get the best provider at the lowest price. In my experience, clients end up paying more for the service than they would without the recommendation of their IT Services provider.