Why does brain control opposite halves of the body?

This picture shows three diagrams.

The circles show the retina, the lines are optic tracts and curved lines resemble the cortex

The third diagram in the picture shows what may have been the arrangement- the right cortex receives visual signals from right eye. But the images on the nasal side will be seen on the temporal retinas of both eyes, which will be seen as double. So the arrangement is not feasible.

Now we come to the first diagram, this is what actually is-

The nasal fibres (carrying impulses of temporal field of vision) cross over. 

And since right cortex receives impulses from left side, it sends motor impulses also to the left side

Now here is my question-

Why don't the temporal fibres cross?

If that would happen, the same half of brain will control same side of the body! Human anatomy could have been so much simple 

If you get answer to this question-

Plz post it as comments 

Thanking you

The human brain

   We humans are the most evolved children of Mother Earth.  Man has dominated the planet since eons and will continue to. But what has made a man so powerful!?

   Man does not have the strength of an elephant, the speed and agility of a cheetah, neither the ability to fly like birds, the sharp claws of a tiger, the venom of a snake, night vision of an owl, ability to camouflage like chameleon, and the list is endless...

   But what is it that has allowed man to dominate all the five kingdoms of life? It's his ability to think, invent, discover, decipher, ponder, wonder, create, dream and realize the dreams. It's our well developed brain!

  So, Our brain is a master piece. No doubt...

It helped us create- machines with the strength more than hundreds of elephants, cars that ensure quick mobility, aeroplanes that breach the speed of sound barrier, prehensively created tools sharper than anything,  chemicals and bombs poisonous enough to wipe off the last bit of mankind, camera for night vision, computers to manipulate, calculate and formulate. 

   We have used brains to solve many mysteries. But the irony is, we don't know many whys and how's about our own nervous system!! We have many open questions in this field, challenging you to take the plunge and solve them. Like-

   •What are dreams? Why to we get them? Why is it that we see that particular dream that we see?

   • why is nature of people different? What controls emotions?

   •why does right side of the body control the left side and vice versa?

   •why some are more intelligent than others?

   •which part of brain is responsible for a particular action?

   •why nerve cells do not regenerate?

   •what part of the brain is the real "you". Where is the soul in our body?!

   •how is a thought or a new idea generated! I mean, it's something big out of nothing!!! How does it happen!?

   •what part in my brain provoked me to write this blog?

The mysteries about our own nervous system are such that our own nervous system is unable to solve so many mysteries about its functioning. 

So is our brain so complicated that our complicated brain cannot understand itself!?

Or is it possible that will evolution make our brains even more complicated that will help us understand it one day or will it make it even more difficult to understand it!?

 The purpose of this blog was to strike a spark of thought in your brain, and just think about it- how is a thought being generated in me...