As per Hinduism, why do heaven and hell exist when the soul has rebirth?

[An online question brought to Swami by Śrī Anil.]

Swami replied: Rewarding souls for their good deeds and punishing them for their sins are done in heaven and hell separately. These worlds meant for enjoyment and punishment are kept separate so that the soul, during its human life on earth, can put forth efforts to achieve spiritual progress, without any distractions. The chance to develop spiritually during their human birth must be open to all, without any disturbance caused by the rewards and punishments. Of course, intense good deeds and intense sins committed by the soul in the present birth yield their respective fruits immediately on earth itself.