If we're talking about having them all having access to each other, then I can't see what you gain by putting apps in different VMs.
And in my writing side projects, I may leave a project for several months. So that's where I realized the value of VM's - the one's I use have survived an upgrade from XP to 7 with the same open windows and without any software reinstallation (and of course without any recreation of bookmarks). I'll add that they are also descendents of previous virtual machines used for the same purpose but different projects. It is more efficient from a workflow perspective to have six copies of Open Office each pointing to the relevant context than to reconfigure one copy each time the context switches.
To put it another way, the way in which one develops software projects from a custom starting point and the way in which references persist across IDE sessions during a project due to saved state are not unique to software development. They are indicators of the features which facilitate efficient project execution timelines.