Minor marriages are a problem because they more often result in divorce than marriages between older people. It is difficult for a marriage between minors to survive because the parties involved are still growing, changing, and maturing. It is not logical to expect most minors to be capable of the commitments and work that building a marriage involve. They may also not be aware of birth control methods which could result in the marriage producing children before the couple is ready for parenthood. This could lead to child abuse or abandonment.
I think that minors should not be allowed to get married, regardless if they have parental consent or not. Children under the age of eighteen are still developing and their brain is not done growing. Children have been show to make impulsive and rash decisions they regret later on in life. Marriage is not something that should be entered into lightly and children to not have the capacity or forethought to understand what a large decision marriage is.
The simplest reason that minor marriages are a problem is that they are very likely to fail. Whatever reason there was to get married before the age of 18 (either a pregnancy, family expectations, or simply being in love), that reason does not seem to be sufficient to keep these marriages together. In the United States, 48% of marriages in which the bride is under the age of 18 end in divorce within 10 years. This is in comparison to 24% when the bride is over the age of 25. The fact that minor marriages fail at twice the rate of others implies that they are a problem.
I do not believe minor marriages are a problem. I believe the younger generation is less concerned about marriage. They've grown up in broken homes, lived through divorces, and found through experience that living together is basically the same thing. I believe marriage rates will more than likely drop over the next decade.
When two people are truly in love with each other there will be more respect and love. If you are young and want to get married go ahead and do this. Back in the old days teenagers were married at the age of 14. They survived through the good and the bad times, but back then they had a lot more morals than we do today, which have been lost.