Marriages in the womb? Why not? It’s all done in heaven prebirth anyway! Marrying young is so enviably simple! I betcha all the goyim would dream themselves such a smooth and guaranteed betrothal.
In conversation with some Chasidim who are capable of a degree of self-criticism (in itself a sign of great deviance) I’ve heard that one of the biggest problems with the system is that children are married off when they are still… children. Some have suggested that the first thing that needs to change is an extension on the age of marriage. Between 18 and 21 one can mature quite a bit, gain insight into life and have enjoyed some youthful freedom.
Personally, I can’t see how pushing arranged marriage off by a year or two will address the issues of incompatibility with arranged partner spouses, postnuptial marital discord, lack of youthful experimentation and premature parenting.. As far as I see, young boys and girls itch to get married young because it is one of the most exciting events that Chasidic children can look forward to. Additionally, life in Yeshiva is terribly boring and boys want to get out of there sooner rather than later. I have known plenty of twenty years old who were desperate down to their white hairs when they were still on the market, waiting for the pinnacle of life’s happiness as they entered their twenties. The system of schooling, yeshiva and the culmination of youthful happiness in marriage, ensures that the Chasidic youths perpetuate the system of teen marriages..
There’s also the issue of sexual release; since only monogamous sexual activity within the framework of marriage is permitted, Chasidim believe that marriage at a young age will provide an opportunity for youths to fulfill their sexual needs in a religiously acceptable way. I don’t know how the Litvish and MO saints manage so many peak sexual years of abstinence, but I do understand that this kind of abstinence gives room for a lot of deviance. People who can’t express themselves sexually in acceptable ways will very likely do it in ways society does not consider acceptable.
I believe there’s also a historical factor to marriages at a young age. Marriage used to be the institution through which children are prepared for life and given an economic headstart. The dowry was meant to support the couple, and during the residency with the parents for the first few years after they got married, they usually learned a trade and began their own business. Parents, who died at a much younger age, may have been eager to see their children settled financially. There were also the infamous Cantonists, young children drafted to the army (or kidnapped by “Khappers”), and perhaps parents quickly married off their children to circumvent the draft. Of course, these motives may serve no purpose anymore, but the tradition of marrying young has clearly survived.