Collective control does not equal you controlling it. FOSS has significant advantage on this front because if you want to you can at least go peek under the covers and see what's happening, but unless you are running a very, very minimal system and very carefully selecting your software and very carefully inspecting every update, you have already given up your control. We all do. And I absolutely know what I'm talking about I manage thousands of systems, both windows and Linux. I work with open source and closed source software. Sometimes the closed source software is leaps and bounds ahead of FOSS. And as a business you choose what allows your business to make money within acceptable risk levels.

I'll give you an example. There is literally no actual FOSS competitor to Exchange (on-prem) for enterprise scale email that functions even half as well. Does exchange suck for many reasons including that it's closed source? Sure. But there's a reason that no one has been able to put forth a reasonable competitor for businesses to adopt and use. There are certainly other options with fewer features or which require you to give up even more control of your data but none that match. So most massive scale businesses continue to choose exchange.