50% of all US marriages end in divorce. I would say it's partly the poor judgment of youth; mine wasn't so good. Maybe it has always been true, but now it is easier to get out. Romance is a pretty poor basis for a marriage. With mutual respect comes love and a more lasting relationship. Consider all the other qualities needed for success. Starting companies is a huge commitment and raising children is an unbelievable…
Also, "all US marriages" is not the same thing as "all US first marriages." A person divorced twice and divorcing for the third time is different from a person divorcing for the first time. That has little to do with the poor judgment of youth.