I don't know the answer. I would say why not, obviously its happening anyway and all by itself. But people are always wanting to know "why?" How did it come to arise that i'm here right now?
The problem seems to come about when you take youself "you" to be what you really are, many people don't know what they are to start with, other than what they see staring back in the mirror. When you were born into human form, our beingness becomes attached, first by "I am John, I am a male", we are identifyed with our bodys, this is all reinforced from life and we begin to become more and more an individual through its conditioning, from our parents, schools, and pretty much nearly everything in life our minds are conditioned, and of cause not only are our minds conditioned but also our bodys eg. lungs conditioned to breath the air, heart conditioned to pump the blood to feed the muscles that are conditioned to move our legs that are conditioned to walk the earth.
In our minds we really become a experience of all our conceptions. Its not that you are seeing the world how it really is, you are seeing the world how you take yourself to be.
To come up with a reason why we are alive I could only guess that, for some reason our beingness, our awareness is fascinated with experiencing itself and by identifying with our bodys minds, you can see it becomes necessary this way for it to get a taste of experiencing devertity.