Hearing "Srimad-Bhagavatam" is a very powerful spiritual practice. Spiritual practice is supposed to purify us from the contamination of our karma. We are spirit souls but we have a very deeply rooted desire to enjoy matter. We can only become happy if we are in contact with some spiritual happiness. Hearing "Srimad-Bhagavatam" destroys our misconceptions and purifies us.
Everyone wants to be happy and material world offers us different recipes of happiness, and we are foolish enough to take them seriously. Therefore we need purification from all these misconceptions. We have a very deeply rooted problem – indifference to the Lord. Even if people believe in God they are not interested in Him.
When we hear "Srimad-Bhagavatam" from Krisna’s devotees, then the true friend of ours, who is residing within our heart, starts cleansing the heart. We should hear "Srimad-Bhagavatam" because the Lord wants us to hear it, but not to do it as a matter of ritual.
If we hear "Srimad-Bhagavatam" properly it goes very deep within our consciousness and changes connections within our brain. The hearing of "Srimad-Bhagavatam" can be successful if the speaker does not have some ulterior motive, but he just wants to give the Supreme Lord to his listeners and he has realization of happiness. When you hear "Bhagavatam" properly from somebody who is self-realized, you become cleansed and will never give up the lotus feet of the Lord. When we get connection with Krisna, He enters our heart and we feel that there is no need to give up on Him, whether external circumstances are favorable or not. The same is with preaching, when someone starts preaching about Krisna, he will never give it up despite all the difficulties because connection with Krisna is there.