Not Op but there’s a inch of people asking why, and I have a similar feeling to op so here’s my post hoc justification for a weakly held and poorly supported prejudice:

It’s really because statistically, in my experience people without kids are more selfish than those without. This is more in description than judgement, but it’s true in my experience. We can speculate as to reasons, but looking after kids does train a certain kind of selflessness. Agreed we might be doing it for ultimately selfish reasons (self presentational or for care in old age or whatever). But for a good chunk of the time, caring for kids seems to require the fairly consistent subjugation of personal preferences, and a degeee of perspective taking, that I just think people without kids don’t have. And that often shows in their interactions at work and in daily life. Obviously there are myriad exceptions. But it’s true enough in my experience.

The wanting to live forever part also seems weird to me, and correlated with a certain sort of self regarding perspective. It seems obvious to me that I (or my generations) need to die for my children and grandchildren to have a good life. To try and subvert that also seems selfish or self important somehow.

I’m not really arguing this is a correct or good or just position. It might be terrible! But it did resonate..