There are many reason "why" we believe in God. I couldn't possibly give you all of them. Some were raised to believe in Him and have never questioned it. Some people have been at a very critical point in their life where only a 'miracle" can explain the outcome. Others believe in someone more powerful, more insightful and omnipresent to explain such things as creation and the "un-explainable".
Note: Not believing in God, doesn't mean He's not real.
You ask why do Christian's believe in God:The secret is when a person comes under the wooing
or unease when the true Word of God is spoken,by personal testimony, pastor who speaks
truths of Word,( Example) Billy Graham, he always had a 3 point sermon ( 1 ) We are all sinner's
( 2 ) confess or admit to Jesus you have sinned ( 3 ) believe that he is Almighty God in Human Body, ask him sincerely to come in your Life and change you The SECRET(,God opens your spiritual senses and it is like a puzzle that finally get;s put together) Your question WHY: Because
he tugs on your heartstrings showing himself real and belief sky rockets
Because there is no way that this earth could be created from nothing and by accident. There is so much order in life (apart from man messing it up) that there has to be a designer who created it all.
I have faith in a creator from the evidence I see in life.
I have faith in the Word of God from the evidence I see in history.
I have faith in my Saviour Jesus Christ because He is the only one who has paid the price for my sin.
And I'm looking forward to spending eternity with Him.
I've found God recently and feel a whole lot better for it.
Beats me. I suspect that most simply follow whatever religion they were raised in, without much thought or real conviction, just a social convenience. Others are no doubt preyed upon by religious types while very vulnerable at a low spot in their lives, while some are simply demented (think Pentecostal and JW here).
We can't tell you why! There are so many reasons why God is so GREAT!