Yros, find me 21 year old boys who are serious about learning, have a strong relationship with HKB”H and a rebbe, who are prepared to take on ALL the responsibilities of marriage.
As it is, for some reason over the last generation it has become much more widely accepted to support for x number of years. If boys will start dating earlier, say 2 years earlier, it will become x+2. Not necessarily good for the shalom bayis of the young couple, and may not help the parents much easier.