Put it this way - animation is costly and time consuming. Cheaper animation looks, er, cheap.
CGI will continue to get cheaper, especially when used with motion capture. Take the copious amounts of telesnaps, map them into 3D, use motion capture suits to insert the actors and you are there. the very next best thing to finding the episodes, and within a few years, affordable.
You're drawing a nonexistent distinction. CGI is
animation. Indeed, all 2D animation is done on computers these days. And 3D animation is even harder to do well than 2D. Cheap 3D CGI looks horrible. You really need a feature-film budget and schedule and the resources and talent of Pixar or Weta or James Cameron to do it convincingly. It's not even remotely as simple as "scan it and there you are." If you think motion capture automatically looks good, you should try watching Polar Express
It's very, very hard to get computers to depict anything that isn't impossibly, mathematically smooth and perfect. Imparting realistic texture, weight, and motion to a 3D CG construct, and doing it well enough to avoid the creep factor of the uncanny valley, is immensely difficult and requires a great deal of hard work from very talented artists. Even the most sophisticated performance-capture technology we have today still requires the frame-by-frame mediation of skilled animators to compensate for the computers' limitations and add in the details and subtleties that make a CG construct look as believable as possible.
Besides, I think it would be wrong to try to make an episode reconstruction so realistic that it could be mistaken for the real thing. It should be clear that it isn't the real thing, that it's an approximation of something that was lost. It should look like animation.