A friend told me recently that a friend of his (yeah, I know, "friend of a friend" stories are always a bit suspect, but in this case I have no reason to doubt the honesty of my friend) was, at one point in his life, a member of a Christian cult (one of the more secluded ones) in the United States for over 2 years.
Street proselytizing was a very common and frequent custom in this cult. Most of the members, including him, would go to streets to preach the Christian gospel to people. Often they would do this several times a week.
He said that during the 2 years that he kept doing this, not a single person converted nor joined their cult, not via his preaching or anybody else's that he saw. Not a single person.
He said that after he had left the cult, he came to the conclusion that the real reason for street preaching was not to convert people (they all knew quite well deep inside that it was mostly useless), but to strengthen their cult mentality: Being constantly rejected by outsiders, sometimes even with quite harsh words, strengthened their view that they were victims and martyrs, shunned and rejected by the sinful people of this world, and that only inside the cult they could feel welcome, friendly and warm. Outside there all you get is rejection and contempt, inside here you have friends and family, and a welcoming and understanding atmosphere.
When you think about it, this kind of psychological tactic to keep people in the cult is quite clever, yet quite evil at the same time.