Why is pruning synapses and losing gray matter important for brain development?

The process of pruning is important to make the brain more efficient.

When developing, the brain is growing then it will pruning. The pruning process will be influenced by the activity of the children. Synaps that used frequently will be expanding, but synapse that hardly used will be pruned. This way, the organism can adapt and develop useful abilities needed and dump useless abilities.

Pruning makes someone can specialize their abilities in specific studies like music, sports or calculating.