Well let me start it this way... If you need a god given reason to exist, you might as well kill yourself. Because you suck. Sorry was that too harsh?
Let me rephrase... You woke up here.. and nobody with legitimate authority told you anything about what where or why. So you started making assumptions.
Shiva the adiyogi (first yogi) discovered a "hack" in the body....what i mean by hack is that he found that "god" is connected with you, two way connection not one way, we'll get to that in a bit. The buddha explained it (the hack) as form of an escape of the endless cycle of samsara(the endless rebirth with no choice) but god didn't tell you shit personally did he/she/it?
About the two way connection... It means if he can get to you, you can get to him too. They say it is as obvious as the sun and you will laugh at yourself when you see it. I'm waiting to laugh like that.
Now why did god put me here at least??... Well now we are in fishy business. My favourite theory is that he is bored of having a perfect life and wants to see some shit... As he is experiencing us all at once, as us, we just don't see it yet. And we are all bound to see it eventually that's why some Buddhists and yogis choose not to help. It may just take a million more lifetimes of experience.