It is not too hard to notice that the average age of marriage of the middle/upper middle class indian is actually falling. At least it’s lower compared to a generation back.
One reason for that may be that boys nowadays earn “well” quicker. In those days, with mostly government jobs, it took a while for the people to earn enough in order to support a wife. Hence the late marriage. However, nowadays, after the opening up of the economy, even freshers’ salaries (in certain jobs) are enough to support a family, and hence people are getting married earlier.