Every living thing have the instinct to reproduce, but some would fight the urge, and refuse even if it's capable. We, on top of the food chain, have the choice.
Every people around my country almost have the same ideology when it comes to marriage, and why it is important to them. Every time I meet with a relative, an old friend, and few acquaintances, they all have the same reason why I need to marry and have a child. Their reason; I will be needing my child to take care of me when I grow old. It was an absurd reason for me. It's easy to have a child, but the way of his/her life will be uncertain.
I want my child to have an impact to our society, but I am not certain if it will be positive or negative. I want my child to grow, and contribute for the betterment of society, but I have no control over my child's future.
I may consider marriage, but I will not choose to have my own child for now or never.
Individual people do have the choice, but if we all stop having children, then it doesn't matter where we are on the food chain, we will go extinct. I don't think that all humans feel the instinct to reproduce, although I agree that most do. It's always funny to me to heard female acquaintances say that they'll never have children. I have seen so many cases when, just a few years later, they are talking about how they want children. One thing I've learned in my life is that it's not a very good ideas to say such absolutely things about the future. As they say, never say never. I just say, "Right now I feel this way. Maybe in the future I will feel differently, but these are my plans for now." Things change. Love and hormones are powerful things.