kid causes

When considering beginning a family...what is it that goes though people's heads while debating creating a new life? I had a reading for my English class that talked about how so many children fell into these group homes because they wanted to get away from their parents- not necessarily because of abuse, but more often because of neglect. Emotional neglect because their parents were too busy working and then too tired to bother with them, or too drugged out to connect with their kids- so rather than staying in the uncomfortable setting of living with someone you don't care for (much like being in a dorm room...) they opt instead to leave.
It got me wondering what it was that caused people to have kids (disregarding accidents).
No child ever asks to be born. It is no ones fault that they exist, they just happened to be created and forced to live out this existence in whatever body they've been given. But when creating these people- what motivates parents?
Do they think they are proving a vessel for one of the millions of imaginary spirits just waiting for an opportunity to come to this world?
Is it so that they will have someone who needs them to give their life a purpose?
Are they bored and want another person to interact with?
Maybe some parents are ensuring they have their own safety net- someone to look after them in their old age who will care about them more than the nurses in an old folks home.
Or perhaps its just what people do at that time of life, so they might as well join the bandwagon. Don't wanna get left behind.

I recently saw a statistic in my psychology book that said that the majority of marriages decrease in happiness when a child is introduced into the mix. Mostly because of the added stresses- women having too much responsibility for the child and men feeling the burden of providing for everyone. If more couples knew that, most likely, they'd be less happy with their partner once they had a child, would they still do it?
I really am curious as to what drives most people to willingly accept the financial burden a child, plus the responsibility of having to raise your own personal goo bag so it doesn't turn out to be a complete dick and burden on society later in life. And what if you get a bad egg, that continues to be a terror despite all your best efforts?
Maybe its the curiosity of finding out what you'd create- will it get your bad genes in terms of cavities, or maybe it'll inherit your intelligence and now you've provided the world with a fabulous new brain that can improve the world and solve all the problems. (only if you're Sheldon Cooper)
I had thought for a long time that if I ever were to have kids that I'd adopt them- but then i realized that if I can't blame myself for this quirk and that flaw, and take credit for that achievement, well...I'd probably have even less patience for it that if it were my own creation.
Probably genetics are the main motivator- some have come to the conclusion that the point of life is to continue life, and in our own day to day struggles to keep on living the way we'd like, that often seems like the most likely theory.