Most of those answers are bullshyt except for the high debt part. Anyway, these kids are young and most are below the average marriage/child bearing age. Let's see their answers when they are 32 and the clocks are ringing hard.
But besides high student debt, to be honest, the decision to have kids usually rests with the woman. Married or not, she is going to make sure she is on the pill or whatever to prevent pregnancy. A lot of chicks want regular careers or have even higher aspirations and having a kids will screw that up. They are independent and don't see the family model of previous generations as an aspiration, which is fine, it just means later marriage and fewer kids if any.
Some fukk around like dudes do so they don't want to settle down yet until they get worried about the looks and other aging issues and then will hunt dudes down to get hitched. So they wait and by the time they are ready, they are in the mid to late 30s which is why there are so many fertility issues and long waits to get pregnant, etc.
Not trying to put all the onus and fault on females but let's be honest, unless he is later in life 8/10 times it ain't the dude harassing the girl to have kids. Especially under 35.