expense. There is a discussion of it on Doctor Who Forum. The boys at 2E have said it costs too much at the current time to do animations. Of course remember when they colorised The Daemons?, now Planet of the Daleks part 3 is now coming out with new technology not available then.
There is a site that is tad bit 'brusque' hope I spelled that right, but it shows a promo for Web of Fear as an animation. It is brill. Because it is a rather 'sdult' site I wont post it publically, but if anyone wants it, I can send it to you privately. I am not contributing to the delinquency of Who Minors!