Most of these child marriages where there is such a huge age gap are where the family is oppressed or in extreme poverty or the old person is someone influential in his area. Even Islam isn't followed in these cases which clearly state that a marriage cannot happen without the girl's consent and there is no concept of forced marriage. Yet, we see and even in the OP picture, the girl is crying.
The root of the problem is complete disregard of law in this country and failure of enforcing law. People get away with murder, rape and other heinous crimes as long as they have the money to buy judges.
So on top of that, criminalising marriage before age of 18 adds to more problems rather than fixing them. The issue is somewhere else.
There should be a law where the parents and everyone involved who tries to marry a girl without her consent should be punished regardless of her age.
Sadly, in our society the will of the girl isn't given much importance which is against Islam and any modern law.