Why didn't Jesus explain to us all the mysteries? Why didn't he explain the universe, how it came to being, its purpose? Why didn't he talk about our lives, where we come from, what is our purpose here on earth? Why didn't he tell us if there is life somewhere else in this universe? In short, why didn't he show us God's philosophical system?
A child who has not reached a sufficient stage of mental and physical development when he tries to perform school tasks characteristic of that stage and that, which entails a higher level of development. However with proper readiness building procedure, normal development difficulties can be over come.
The people of two thousand years ago did not understand God and the universe as fully as we do. Remember this was before the age of the microscope and the Hubble telescope. The world was flat and was the center of the universe. The stars were holes in God's canopy over the earth. Mental illness was demonic possession. Physical illness was cured by bleeding the patient.
Previous experience determines a child's readiness for learning prior exposure to basic skills is necessary before complex tasks are tackled.
The people of two thousand years ago lacked sufficient experience to fully appreciate God's philosophical system. Today, there are still many people who lack this ability.
Relevance of materials and methods of instruction.
Research has shown that children are more ready to learn materials that meet their needs and fit their already established interests. Children are more ready to learn skills of spelling, reading and
writing when they are having fun doing it.
People of two thousand years ago were too busy meeting needs for food, water and safety to be concerned about God's philosophy. Famines were frequent. Water systems in many communities were no better than open sewers (remember they had no concept of germs). The Romans considered the Hebrews as subhuman and treated them as such. When your every waking moment is filled with these concerns, there's not much time for philosophy.
Jesus taught them as much as they were ready to learn.