Confidentiality and security. Sharing that level of information with outside organizations is just not possible in some situations. Regulated industries need to have full auditable control of all of their data and infrastructure, and a third party does not allow for that.

Even if it was possible for me, I still would not want that level of information out there with a third party. It increases the surface area for an attack, and puts the company at greater risk relying on an unknown level of security which there is no direct control over.