Im not sure that by lowering the age that people usually get married will suddenly effect at what age people mature. It seems difficult to imagine in our society a 21 year old to be ready for so much responsibility.
In todays society and bachur can go until 20 years old without making a real life decision.
When i was growing up, which wasnt that long ago, we took city buses at 9 years old, my Father took a train across 3 states by himself at 8 years old. Now, I know parents that wont let their son take a car service by himself at 15 years old.
I guess if money is not an issue on both sides than they can do it as the parents on both sides can continue to make all the decisions, but in the average case can we expect that “all of a sudden” these children will be grown adults??