You may not have been asked to exist, But God did. Being as it is said that He knew us before we were even born. Now your question is perfectly ligit. and no one knows WHY we were 'chosen' to be born.
This is something we will find out when we meet Him after we die or get raptured. But, we are here on this earth because it is God's will...
Mayhap too if you would stop and think that God chose you for a purpose? like he chose Moses, and other prophets and evangelists to spread the word?
Jeremiah 1:5
“Before I formed you in the womb I knew you, and before you were born I consecrated you; I appointed you a prophet to the nations.”
THIS IS A BIGGEE.......
John 15:16
You did not choose me, but I chose you and appointed you that you should go and bear fruit and that your fruit should abide, so that whatever you ask the Father in my name, he may give it to you.
Now if you were to look at this as a gift and not as a curse, and look around at the beautiful things that God has given us to enjoy, and develop, and use it as ...an ADVENTURE...and each day you get up, and face the world as a Challenge that can be good or bad...Right now if you were to take the opportunity of seeing your life as a blessing and then start exploring it as a GOOD thing, and not as a curse, you may then be able to see the reason WHY God chose you to be born.
You are here now, and YES, you have been given a CHOICE to take this life and run with it with God's help if you were to ASK HIM into your life thus, believe me your questions will be answered by the TEACHER and Guide that He has given all those that seek truth, and peace, and if we have an open heart and mind, you will then see that being 'held responsible' is NOT that difficult. It is no more difficult than the rules of your parents, or the LAWS of the land that we must follow.
Let me ask you something here..WHEN you follow those rules of your parents and the LAws of the land..you find your life a lot easier to live don't you. You have a guide line in which to calm you in times of trouble because you have been taught right from wrong...God's MORAL laws are no different.
So, please realize that life is precious, and if you would allow yourself to enjoy the beauty of God's creations, and guideposts and accept Him into your life as your savior, I PROMISE you that this question will dissolve like bubbles in water.
Jeremiah 29:11
For I know the plans I have for you, declares the Lord, plans for welfare and not for evil, to give you a future and a hope.
Romans 5:1-21
Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ. Through him we have also obtained access by faith into this grace in which we stand, and we rejoice in hope of the glory of God. More than that, we rejoice in our sufferings, knowing that suffering produces endurance, and endurance produces character, and character produces hope, and hope does not put us to shame because God's love has been poured into our hearts through the Holy Spirit who has been given to us. ..
Ephesians 2:10
For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them.
So, stop and think here...you're here now, so, make the best of it....you do have a choice, so you know the right choices...it's easier to do this than fight it.