antinatalism and pessimism

Missing out on a good thing due to non-existence is not even a consideration, because you have to be born in order to be deprived of anything. Pleasure in life is mainly defined in terms of relief from deprivation. I suppose you could challenge the idea that missing out on a bad thing due to non-existence is 'good' (given that nobody can perceive the good). But it's at least completely avoiding the bad, without having unasked risks taken with your wellbeing by someone else.