Some women don't want to wait until it's too late to reproduce. Its many reasons why there are so many OOW kids. Some would rather have kids in their 20s and 30s versus waiting until they in a age range when they are less fertile or they catch an incurable STD that could hurt their chances of having kids.
Also, some folks fall in love or lust too early and later realize that their baby dad/mom isn't a long term solution or marriage material. Just cuz u reproduce with someone doesn't mean they are a decent or even suitable and compatible partner/spouse for u. It may sucks for the kids who would be better off in a 2 parent home but that's life. Sometimes folks gotta do what makes them happy. I just think folks should try to get along and co-parent to the best of their ability.
Also, some families pressure their kids/family members to reproduce at a timely rate. But again...that should be determined by the potential parents and their ability to have kids...but with life...sometimes things don't come at ur time. U know the religious saying...he may not come when u want him but he'll be there right on time.
I honestly envy some of those who had a kid or kids in their 20s and early 30s because u never know how long u gonna be around, how ur health will prevail and u will be likely around to raise and bond with ur seed.