I think many people feel they are incapable of taking care of offspring. Better not to bring into this world children you cannot care properly for.
The reason people choose to have less and less kids is because raising a child is a thankless/tough job and despite all the progress that has been made on the social aspect of raising kids, more often than not, it is still the woman's job to do the rearing and raising of the kids.
Family is not everything, I know countless people who were born in terrible families.
Leaving a legacy is so overrated, why do you feel like you need to do so? What is so important and so unique about you that if your family line were to end today, the world would be missing?
Please don't confuse your opinion with facts.
What is sad to me is people like you who think they got it all figured it out because you decided to procreate. Condescending much?
People commit the worst atrocities and embody a dog eat dog mentality, all 'for their lineage' or 'family'. Borges said that procreation is a mirror, I agree. To me, it only serves to multiply and if you're not careful, ie, you think you'll finally have 'meaning', you'll probably be eaten alive.
But of course, if you aren't thinking about it, and those questions are never broached and the 'genie' isn't out of the bottle. Well, I wish I was like you then haha
Its societal pressures. Our society has changed fundamentally, look at any graph, income inequality, household earning power, household debt, etc.
You can't blame animals who go extinct due to deforestation and habitat loss and say "it's sad they chose to not reproduce"