If you're seriously asking yourself this, let me refer you to Mr. Darwin.
I get that people have myriad reasons for not having kids, and I truly respect those reasons, whatever they may be.
But if you throw your hands in the air and say, "Gosh! This is horrible! How irresponsible to bring children into this world!", fine. I'm OK with that. I really am. You're kind of a pussy, but I'm fine with that.
OTOH, my genes will outlive yours, because they're tougher, selfish. This is Biology 101. Maybe check out Dawkin's The Selfish Gene, because that's how the world works. It's simple science, evolution.
tl;dr: I've never given two fucks if my line continues, none, never a thought. But give up a billion years of perfect heritage if you wish. I will not. My children will inherit the Earth, while your line dies. I'm ambivalent on the question, done my part. Roll the dice!