Songs in TF are an important component of movies. Movies and songs are inseparable. TM has survived solely, because of movies. Songs are long remembered after the movie is forgotten. We all know Paalum Pazhamum has excellent songs, but how many of us care for the movie.
Songs give that immortality.
On the other hand, many a time songs have been a distraction to the story. Song sequences are used by many to go to the washroom. Even this can be broken down by directors such as KB, who exploit songs to their fullest capacities. Generally one to two songs in a movie serve its purpose. Songs in TF are an excuse for the wildest of imaginations.