Git is for version control, not deployment
Git is for developers to manage their code, not to deploy code. PaaS (platform as a service/software) is a black box unless you understand that you wrestle control with the provider and trust their service.
A black box is worse than a leaky abstraction.
While an abstraction lets you break the walls if you need to, a black box effectively locks you out of a particular software or service. This is the knowledge asymmetry that the provider wants to leverage since you need to go for your checkbook just to unlock what you need, instead of doing it yourself.