Why Saints descend?

Swami Gnanananda Giri lived in Tapovanam, near a place called Tirukkovilur in Tamil Nadu. Often, devotees used to come to him and share with him their problems, personal weaknesses and the sins they have committed. Swamiji would listen to all of them patiently and bless them with a lot of goodness.
Once, a close aide of Swamiji asked him, ‘Swamiji, Why are you taking the sins and sufferings of the devotees and giving them ‘punya’ (merits) in return?’
With a smile, Swamiji answered, ‘We often see in streets men who come door to door to collect waste paper, bottles and other trash from each house, don’t we? The householders also collect the trash from their house at regular intervals and wait for the person to come and collect it. When the person shows up, both are happy. The householder is happy because he gets rid of the waste material in the house in return for some money. The trash-man is happy because he got some trash for the day.
Likewise, saints come down on the earth to take the sins accumulated by humans at regular intervals and bless them with goodness in return.’