What could motivate a soul to get into such body?
The human body is high maintenance. It needs to be fed three times a day. It has to be cleaned every day. It must be kept at the right temperature. Nails and hair need to be trimmed. You have to take this body to the doctor, the oculist, the dentist. You even need to build hospitals in case of emergency. The best you can expect after all this tender loving care is that it does not hurt! We are prisoner of our senses, prisoner of our body and prisoner of our limited consciousness. What could possibly attract a normal soul to such a body?
Body and soul can get separated and put back together again.
It happens every day in the operating rooms. “We lost him” said the surgeon. The patient does not have any blood pressure. No pulse. No breathing. No electrical signals in the brain. That may last 10 minutes – half an hour – sometimes more. Instead of sending the dead body to the morgue the surgeon and his team can, sometimes, reunite the body and its soul. Some patients remain conscious during the whole time. When the surgeon pays them a visit a few days later they can describe everything that happened. They can repeat what he said, describe the tools that he used. They were above the operating table, watching people working on some body. They could move from one place to another just by thinking of another location. Search You Tube for Near Dearth Experience and have a round trip ticket to the world of the dead.
This is something we may consider when we are looking for life on another planet. If we can have a body without a soul we could also have a soul without a body. What could prevent a planet from being inhabited by souls without a body? We are looking for water because our own body needs water. That does not mean that everybody on any planet should use a body made of water. The world may not have been created in our image.
Consciousness is restoring the links between the pieces.
This is the opposite of the way astronomers see the world. They start with the unity of the Big Bang and describe a universe falling apart.

They call it an increase of entropy leading to more and more chaos. Developing consciousness is following the same path but in reverse. When you break a cookie into two, you get the two pieces and the link between them. Consciousness is restoring the links between the pieces.
First answer
Let’s get together the clues that we have, so far, and make a theory.
It could be possible that during the day we associate ideas with the energy that we get from the plants. Our limited consciousness does not let us get much further. The best we can do is to assemble our problems with some energy and send them to the hippocampus. At night the brain is free from the limitations of the body. We have full use of all our neurons. We can use the energy sent to the brain to process our problems. The result is an increase of consciousness. To solve a problem is to get conscious of its solution. It is this increase of consciousness that we will find at our disposal the next morning to solve our problem.
The purpose of our life would be to push the limits of our consciousness. What we call ‘education’ is a gradual increase of consciousness. Slowly, one little step at a time we try to reach above our glass ceiling. We even created our cooking in our image. While following the recipe we associate energy with our food. Then we place it in the oven and wait.
That could explain the slow development of our last 30 000 years. Our main concern was to find food. This was the main problem our brain had to work on at night. That kept us busy at the level of matter. An empty stomach prevails over spirituality. Nobody complained!
We may not be the master of our ship but we are trying to master the wind blowing in our sails. The association of body and soul has two effects. It makes us conscious of the attachment of our soul to the material level. Pain is the way the body gets attention from the soul. The other effect is to give the soul the energy it needs to escape our jail. We get this energy from our food and transform it into an increase of consciousness at night.
Science, religions and the arts could be seen as different attempts to increase consciousness and break our glass ceiling.
Our evolution is speeding up
In the last 200 years the world’s population was multiplied by 10. We developed agriculture. People move to the cities. That created serious problems but communications became easier. It took us 300 000 years to make a bicycle and within a century we went from the bicycler to landing on the moon. Every little increase of consciousness makes the next increase a little easier. After the computers comes A.I. Our development and the world’s population seem to follow the same exponential.
Associating the soul with a body,
gives the soul an opportunity
to free itself from the material world
That would make us part of a general current going through the universe. We have the energy of the sun being absorbed by the plants. This energy is transferred to humans through their food. About 20% of it is used in our brain where it becomes consciousness. This current is moving from matter to the immaterial world and we are part of the process.
What happens next may be above our head. Do we contribute to the general consciousness of the human species? What comes first: consciousness or love? Do we get conscious of love or is it love that makes us conscious?
That may not be a complete explanation to our life’s purpose but it should be part of it.