Um, they wouldn't be as religious if they didn't?
Fear mostly, hope, desperation, brainwashing.

It gives them a ready made purpose to life insted of having to go through the work of finding/developing a purpose of their own.

Also, humans evolved as "herd" animals which congregated in groups for safety. peopel just generally feel safer if htey feel they have a place in a group. That is partly if mot mostly instinctual.

As you read acounts of peopel leavign the religion they were raised in, you will find that many peopel here found it harder to give up their place in teh group than they did to give up the religious beliefs. Again, tht is animal instincts at work. It generally takes higher intelligence to over come animal insticts, which is why atheists are generaly of higher intelligence.

We were informed of a cancer scare in the immediate family today (step daughter). It reminded me that as a believer I used to be able to feel vaguely in control of such situations by praying about it, "committing it to god", etc. But I also can't forget that god NEVER intervened such that things played out differently from random happenstance. Which, after the initial dopamine hit of minor comfort, always turned to frustration, disappointment, and a deep sense of betrayal.

What I did today was tell my wife we have no control over these outcomes, and we just have to put it aside and hope for the best. Which is all anyone ACTUALLY does anyway.

But to answer your question, people invent gods because it's a way to "understand" the incomprehensible and "endure" the unendurable. Even though all it really does is hold out an empty promise of rendering life comprehensible and tolerable.

I believe man created god/gods in his own image because man could not accept that the world contained things out of his control such as disease, storms, earthquakes, death. This way they could rationalize that there WAS someone in control, someone quite a bit like them but omnipotent and omniscient. When they couldn't understand why this "sky daddy" would allow or even cause terrible things to happen they decided it was because they were too limited to understand the reasoning of this made-up "god". In the polytheistic Greek and Roman cultures the gods were even more like us, petty and jealous and cruel and vindictive as well as loving and kind, just like the God of the Old Testament. This crutch is passed from generation to generation to insure the safety of the believers' offspring; since they really believe in their God and all their Holy Bible says about him, not indoctrinating their children would guarantee those children an eternity in hell.

Indoctriantion is the reason. If we were not instructed with this nonsense from birth, I don't think there would be a need for any God worshipping. Just like drug dealers...create a need, then let the addiction take over.

If you are asking why people NEED a personal god to believe in and talk (pray) to, as opposed to philosophically believing in an impersonal creator of some sort, you are essentially asking why some people need a perfect parent in the sky to make sense of their lives, and to console them in the face of the injustices of this world. (Sigmund Freud had quite a bit to say on this subject.) Also, some people cannot bring themselves to accept that this crazy world is all that there is. I've know several people to say that God must exist, or the Gospel must be true, because it would be too depressing to think otherwise. I've also read that the only question that truly divides the religious from the non-religious is: "If you found out tomorrow that God did not exist, would life still be worth living?"
Guess who says "yes" and guess who says "no".

Who cares. They sit around and try to figure out why every athiest doesnt believe in god and agnostics don't convert to christianity. then if they don't have that to challenge, they can't understand catholics or any other faith than their own. If their circle is so small that it is only people of their own faith and church that they know, then they question anothers faith, commitment, how they live. A shift in humanity has directed people to livinglike this and continually peeking over the fence at everyone else.

They need something to make them feel secure. they can't just let go and believe in what they do.

I think you might be better asking that to a theist. I can hypothesise, but it would unfair for me to speak on behalf of theists.