Because it changes life for most of us
you do not have to be religious and living in a religious country and your life will be effected by it
we may try to keep politics and life out of religion sometimes we can sometimes we cant
No god is enough for any of us to provide fulfillment in our lives or to give purpose but the values that comes with the god and the religion makes peoples life better.
remember religions came unto this earth due to illiteracy and poverty and injustice and some way for ruler to emphasize their rule on the people but still does effect most of the people living in poverty on much of the world
may god does not exist but the notion bring people to calm and still is predominantly needed for much of the world society