Jesus explained a lot of things to his disciples, including, interestingly, an explanation as to why so many (more than a majority) experienced no lasting effect from the preaching of the Gospel. Here’s what he said:
“That same day, Jesus left the house and sat by the lakeside, but such large crowds gathered round him that he got into a boat and sat there. The people all stood on the shore, and he told them many things in parables. He said, ‘Listen, a sower went out to sow. As he sowed, some seeds fell on the edge of the path, and the birds came and ate them up. Others fell on patches of rock where they found little soil and sprang up at once, because there was no depth of earth; but as soon as the sun came up they were scorched and, not having any roots, they withered away. Others fell among thorns, and the thorns grew up and choked them. Others fell on rich soil and produced their crop, some a hundredfold, some sixty, some thirty. Anyone who has ears should listen!'”
His disciples weren’t sure of his meaning, so he explained it to them:
“‘So pay attention to the parable of the sower. When anyone hears the word of the kingdom without understanding, the Evil One comes and carries off what was sown in his heart: this is the seed sown on the edge of the path. The seed sown on patches of rock is someone who hears the word and welcomes it at once with joy. But such a person has no root deep down and does not last; should some trial come, or some persecution on account of the word, at once he falls away. The seed sown in thorns is someone who hears the word, but the worry of the world and the lure of riches choke the word and so it produces nothing. And the seed sown in rich soil is someone who hears the word and understands it; this is the one who yields a harvest and produces now a hundredfold, now sixty, now thirty.'” (Matt. 13:1-9,18-23)
25% of those who hear are robbed by the Evil one and nothing ever comes of it. 25% of those who hear are unwilling to endure any difficulties or persecutions and they abandon what they’ve heard. 25% are more concerned with the flesh and the world than they are with the Gospel and they turn away. And a mere 25% become productive members of the community of faith.
In simpler terms, 75% don’t really ever become dedicated disciples. Not because they can’t, but because they wish not to be. Those who do though, they are instruments of God in a lost world.