In my opinion, most tech-like professionals miss the point of delegating liabilities.

The whole reason to pay for software is to offload the liability to a 3rd-party. In simpler words: "As a company, I have this need and I don't want to solve it myself. Also, if I pay someone, I can sue them on contract breach just in case."

The legal part of the liability offload is key in the decision, because it requires ownership.

FOSS doesn't fulfill that requirement, therefore, adopting FOSS means the user owns the liability of using the software. Companies don't need or want more liability than they currently have to, less is better.