there is to much information to decode to show it in a screen like tv, there's to much going on to see it in just 3 or 4 screens, think of it as surveillance sistem, but instead of having 10screens showing different angles, you have 1 to 3 showing everything at the same time, if you understand the code, you don't really have to see it decoded
no, if you will pay attention, everytime they switch between different scenes, different people, they have to move to a different code...each screen can show only so much information...thus, only a small FRACTION of what is in the matrix can be seen by any human at any time...not even the agents know where everyone is at any time...