Some might say this is selfish, but on the other hand it’s kind of weird to expect anybody to commit to that for the sake of some other party, whether that be society, the government, peers, or parents, particularly when none of them are doing anything of substance to help mitigate those impacts in exchange.
And that’s without even touching the financial security angle. It’s unpleasant to have to struggle and scrape by as an adult, but absolutely terrifying when there’s children involved, and for most couples the likelihood that they’ll need to struggle at some point is much higher if they have children. It’s understandable that people don’t want to risk that if they don’t absolutely have to.