Why no gravity models? How long must we wait?

Rating: Null/10 (14 August 2011)

I can't understand it - a film company spends millions on CGI to make the apes look realistic when motionless, but as soon as they move, their pathetically inaccurate gravity and inertia models are revealed for all the world to see, thus rendering all their (huge) work on making the apes look realistic, a total waste of time, because they are then obviously unreal.
Why is it that after twenty or thirty years of CGI, the companies responsible for it still don't use accurate gravity and inertia models? How on earth do they manage to create gravity and inertia models that AREN'T realistic? All you need to do is use the basic physics equations which we all learnt in school, and you have perfect, realistic movement. So why aren't they using them? Why do they deliberately handicap their own CGI, so that it doesn't look realistic? Just look at Gollum in LOTR: why did they ruin the film with the same unrealistic gravity and inertia models? As a result, this film is yet another one which is totally ruined for me.
I had realistic gravity models on my 386, over fifteen years ago - maybe it's twenty years, I can't remember. Perfect models of bouncing balls, totally realistic, simple code, so why are these film companies not using the same equations? Anybody?