Why do some people believe in a higher power?
Most people need faith in a higher power. It is comforting to think that there is an eternal life of bliss. Believing in life after death gives a calm assurance that there is more to life than what we experience on earth. It is reassuring to think that life will continue in a much more peaceful environment than the one we live in on earth. To think of a place called Heaven where there will be no racism or violence is a comforting belief. Life forever with no pain is a comforting belief. For many, belief in God and a place he has prepared for his saints is such a peaceful feeling.
For those who believe in the Christian Holy Bible, there is a place where God is preparing for his saints--those who are believers in Jesus Christ. In John 14, it states that Jesus has gone away to prepare a place and he will return for his saints one day. That promise is so reassuring. "Let not your heart be troubled..."
I would say that not some but most people believe in higher power. The analogy can be seen in the international politics. There have been always a struggle to be the higher power by nations to command and control the world and to become a supreme power. The existance as a supreme power gives a feeling of security to the nation herself and to the other nations who are, or want to be, an ally of the so called supreme power. How false this feeling may be as one can see by the fall of great empires in the history of nations, the desire is always there.
In religion, the higher power rather the Highest Power is the God. The attachment with Him provides the extreme sense of security and peace of mind to people who believe, surely not that extent to the people who say they believe. They know that there is Someone who will come to help when they call Him and that is why they believe in Him for He is The All-Mighty, All-Merciful.
Belief in a higher power gives us a sense of someone guiding us.
The higher power can be in the form of God, the principle of Non-violence, Scientific truth etc. -- Belief in any of these can be a motivator for us to go beyond what is known. Such a belief will also make us humble.
Some people believe in a higher power b/c they need someone to workshop. If we don't have a higher power, then we don't have the guidelines to follow.