Configuring services from sidebar is out of context
Reframing #6782 based on Jordan's explanation:
If you click on the NFS wrench icon, or the iSCSI wrench icon, you are not asked whether or not you want to enable the service. SSH is the same way, and therefore self-consistent. It would be weird to add a pop-up dialog for that one case.
This makes perfect sense, if you're on the Services tab with the wrench icons.
But the problem (such as it is) is that the left sidebar lists all of the services, and clicking on them brings up a pop-up window to configure that service, regardless of whether you're in the Services tab.
Maybe clicking OK on one of those pop-up windows should take you to the Services tab if you're not there already? Then you'd have the on/off switch right in front of you, as Jordan describes.