A drawing does not need to be open to use the VBA environment, however, a drawing does need to be open to enable the environment.
Consider this:
Load the previously attached acad.dvb and create an event for opening a drawing and/or creating a new drawing.
Save the dvb
Close AutoCAD
Re-open AutoCAD, note that no events fire as the first drawing is already open by the time the VBA environment initializes.
Close that drawing so there are no drawings currently open, presumably the VBA environment is now inactive.
Create a new drawing, note how the events fire just prior to refreshing the window.
Another exercise is to create a timer module that sets a system timer. Set the timer to call a macro to pop up a window every minute. Run the timer macro and close all open drawings. Presumably the timer would not be able to find the macro to call if the VBA environment is inactive while there are no drawings open, but it does fire, and it does find the macro.