Think of film the way you think of a press ad. Nobody likes a crowded press ad and there is no reason why a film should be different.
Very often I get TVC scripts where the writer, probably after the client has clobbered him/her on the head, has written about 5 or 7 great attributes of a product. It is possible that they may all be true; however, to effectively communicate it all through a 30 second TVC might need a superman of a film. And we all know how few films fit into that category. The upshot is that all 5 messages will be communicated in a kichdi form. Of course your client will be happy but the film will get lost amongst a million similar films. If you are writing a film it is very important to have a clear goal and a singular message. Most commercials lose sight of this basic fact. Clients will try to maximize the opportunity by adding as much information as they can, but a smart writer knows just how much is enough. Wear a helmet to work but stick to your guns, reject all briefs that ask you to do more than one thing in a single piece of creative.
The logic that the film is going to run a million times and all 5 messages will come through because of repeated hammering is flawed. The consumer is simply going to switch off.