Why do you have religion?

The reason why there are religions is because people had traditions and beliefs that eventually became formalized. Religion was created as a social compact between man and the universe. They created a God that would bring psychological comfort in times of hardship. They created a God that would protect them from natural disasters, disease and extinction.
Religion provided the method for maintaining social balance.


Answer

Because that's how we label the different practices that people with common ideas or beliefs about God.

Answer

The real problem with 'religion' is that many of the rules within most organised religions are man-made. Despite being a Christian I hate it when someone calls me 'religious' as I'm not. I always equate 'being religious' as being 'holier-than-thou' and, somehow 'better' than the irreligious - again which I'm not. All too often in historym, organised religions have had a great deal of explaining to do as their man-made rules have won causing hatred and oppression rather than showing unconditional love; to look for real, Christian love, one invariably has to look at individuals rarther than organised religion.

If the question means 'why do you have organised religions' this is simple because, as the above answer states, people had traditions and beliefs that eventually became formalised. However, because major religions are run by humanity, they are susceptible to corruption and causing misery just like any other large organisation, just as much as they are capable of great good for the whole of humanity both here and now and in the future.

However, if you mean 'why do you (personally) have your own belief, then this is quite different. Almost everyone has some degree of spirituality, even atheists, for even in denying a God they are considering the question as to whether there is a God or not. Speaking as a Christian, Christians have a special belief in, and relationship with, God through Jesus Christ. They believe that this relationship is so vital for life and brings life in all its fullness to those who follow him. They seek to improve their lives and the lives of others by following two simple commandments - to love God with all their heart just as he loves us, and to then share this love with others - unconditionally - with as much sincerity as we would love ourselves.

If everyone followed these two simple rules of life then, surely the world would be a much better place.

So really, religion isn't important. It's the relationship with God and what we do with it that really matters.