If you are an anti-natalist and think being alive is hell and suffering and an overwhelming bummer, why are you still alive? Is there some life instinct that's driving you to stick around or you're just not ready to check out yet?I explain:
Let me explain by analogy. Two birthdays ago, my friends had a surprise party for me. I was in a very antisocial mood at the time, and it was a very unpleasant experience - but I suffered through it because I didn't want to hurt my friends' feelings. I didn't just walk out and leave the party (though I feel I morally could have done, if it were bad enough for me). But mostly I wish they hadn't had a party for me in the first place - I would have been better off if they hadn't.In more general terms, the question may be phrased as: If you have been the victim of injustice and a solution to your subjective suffering exists, why not take it? And the answer is: because the proffered solution (a) through no fault of mine, harms others whose interests I care about, and (b) through no fault of mine, will very likely put me in a situation that is worse than my current situation.
Ditto my mom giving birth to me. I wish she hadn't, but my family and friends would be very sad if I peaced out of the party (though I still have a moral right to commit suicide).
Another problem is that killing oneself is hard. Barbiturates are tightly controlled these days. You'd be amazed how easy it is to survive a gunshot wound to the head. And then they keep you alive and do medical experiments on you without your consent. Not a pretty picture.
See also: If You Love Life So Much Why Don't You Marry It?