Why are there so many banner ads during programs free tv australian networks?

its on constantly through programs especially on channel 10. Why the hell are they allowed to do this they have enough ads between programs every 3 minutes why put this on the screen during the show im watching? it takes up too much room and its always advertising the george negus (six millionth news program which dominates all channel 10 programming by the way) I would understand if it was once in a blue moon important breaking news - whats next ads through the whole program including sound?