It used to be, the way you deploy environments involved stripping out the parts you didn't need for your application. This is doable, but it is a pain, and if you do it wrong, your app blows up sometime when you don't expect. ObjectStudio Smalltalk can bootstrap itself from source files, so you can avoid stripping. VisualWorks tries to build itself up from components (Parcels) on a base image as a deployment strategy. These are less painful than stripping, but your app still blows up if you do them wrong.
Combine that with some vendors not being all that concerned about testing deployment, and you have a potential mess.
Image-based deployment done right - have two images. Your devlopment tools go in the second image. To deploy, you simply leave out the 2nd one.
The classic demo -- have your students spend 1/2 hour writing some toy system. Then have them hard-reboot their machines without saving the image. Show them how they can restart the image, grab the Change List tool, and voila, all their source code is back!
To answer your question: it's possible that the source can be absent, but you have to execute an explicit command or do some sort of willful sabotage to make it happen that way. Really, it isn't so different from having separate source and executable files.