It is rude to ignore your elders.
Timmy'a grandmother asks him to get her something from the other room.
Timmy wants to watch TV.
Timmy says okay and gets his grandmother what she wanted from the other room before starting to watch TV.
Timmy goes to the TV and starts watching a show as if he didn't hear his grandmother's request at all.
Timmy's grandmother thinks Timmy is a helpful and polite boy, and she smiles at him.
Timmy's grandmother thinks that he is incredibly rude for not responding to her when she needs help.