>>You'll see that Jesus spoke to multitudes but only committed his deeper teaching for his disciples<<
Because he knew his time was short - which is why he instructed his disciples to teach others. The Great Commission springs immediately to mind.
Paul's numerous letters all contain instruction to the individuals or churches to train, teach, grow, and exhort others in righteousness. Christianity is not for the idle. To start:
Luke 6:4, Matthew 13:52, 1 Peter 2:2, Hebrews 12:11, 2 Peter 3:18, Titus 2:11-13, 2Tim 3:16, 1 Cor 3:7, 1 Tim 4:7, and nearly the entire book of Ephesians.
Those who hear the word and accept it are the ones who produce fruit. The rest fall by the wayside.
>>They get saved, get excited and then fade away. But there are other parables that deal with that phenomemon.<<
And as the parable of the sower indicates, they were never truly regenerate in the first place.
First off, YOU are not the judge of the fruit.
Second, not all will produce the same volume and quality of fruit. Some are called to do more than others. Not all have the capacity to do the same.
Third, your understanding of the sower and seed is still shallow.
DO YOU DO EVERYTHING POSSIBLE EVERYDAY TO ADVANCE THE WORK OF THE LORD WITHOUT ANY IDLE OR WASTED TIME OR EFFORT?
If not, you prove my point. We each have callings, capacities, and limits. Some limits may be self imposed.
Are we all eyes, ears, arms or feet? Do we all have the same position or the same mission? The new believer that is blessed to smile and pass out programs on Sunday may be fullfilling his calling just as adequately as the leader of a mega church.
Check out Jesus telling Peter to feed the flock. He's telling him to feed all the sheep, not just some of them.