For those who are just getting started with video or don't have professional work experience. While Tony can take many projects right through finish, editing and production for that matter is much like building a house. When building a house, carpenters do carpentry, electricians do electrical. Production work is very similar, specialists come together to bring their expertise to create the components for the full package. Let's put it this way, considering an editor as one that is the jack of all trades is like considering your hairstylist to do your concrete repairs.
In the post world, editors edit, colorists color, animators animate etc. Certainly many projects can be managed by a one man band, and we do plenty however; those same projects can grow to need specialists to handle their area of expertise.
For example, suddenly you might want more animated text that comes from behind a character, and now with a 3d look. At that point, that work should be handed off to a separate process after picture/story is locked. That type of work is quite tedious and time consuming. The point is that diving into the technical animation when you should be focusing on the timing, pace and content of the moment is not an efficient use of resources or time.