That and we don't even really maintain Retail compatibility. The missions are the closest thing you'll get, but they use backgrounds and other features that are not possible under Retail, so they likely won't work under "Retail" executable, never mind that the Goals, Events and 'meat' of the mission files is still unaltered.
And if we maintained _strict_ retail (As in, FS2 exec) then there wouldn't be much in the way of MediaVPs at all other than some DDSifying of some images because we wouldn't be using the High-Poly models (with nameplates and other Texture Replaceable bits) that we are using today.
The Hatshepsut wasn't the primary reason (though it illustrates a damn good one) for the adjustment made. .10 had more texture breakage changes over previous than .12 has over .10. But until things get ironed out a bit more (read: more models get completed and more efficiently textured) it's going to keep happening. Everything that uses the MediaVPs should be able to continue using the MediaVPs, but there are customizations made, sometimes to a single texture on a ship that are expected to not be changed that when it does change, breaks because of the basic assumption. And it's not that the assumption is wrong or incorrect, it just doesn't hold up on the long term.
And with a project as big and as slow as the MediaVPs and the fact that everybody always wants to work on something OTHER than it (be it a TC or a custom mod with something other than the same-old-models) we don't see a huge amount of progress by compare to others.
FSU SVN: First commit was 10/27/2008. Current Revision #: 518
BP SVN: First Commit was 10/06/2009. Current Revision #: 3659
It's not just that there are new models there, but more range of possibilities. Aside from some texture replacement or background changes or fixing the occasional mistake or model dimension corrections, nothing needs an edit mission wise for the MediaVPs. So that leave us with shaders, tables (when there is a change in the model that requires it), models and effects. And sometimes there are big enough changes between the old and the new that providing a way for people to have the ability to take the time to adjust to those changes is a good idea, however it ends up being handled.