There is no motive in performing kirtana . It is the song and dance of ecstasy, the dance of the soul. Actually, the body cannot dance without the soul. A body without the soul is a dead body. Krishna consciousness is transcendental happiness.
Material happiness is temporary.
One thinks he will be happy with a beautiful wife, girlfriend, boyfriend, bank balance, relatives, house and car. But such happiness is flickering because these things are material, and thus short-lived. We are naturally happy as spirit souls. The soul is ananda. Ananda means bliss.