So devops people would use Bob CD to build their in-house solution for it, and everyone would be using that, without actually using Bob CD directly.
Having an automated process to check out the most recent revision of the codebase and compiling it is just as easy as with other development.
Doing anything with that in an automated process is usually far more difficult. Suppose I'm developing a WiFi thermostat. The flashing process for that may require manual intervention, but let's leave that aside.
So the new code runs, now what? I need a webcam to look at the display, a robot to press the buttons or turn the wheel, and further fixtures to see if it is turning on the furnace appropriately.
Or we could simulate all the hardware in software... do I need to explain how much of a project that in itself is? Sure, it can be done, but it is the old question of time and cost.