Over ten years back, my mother had asked my father when they were going to conduct my thread ceremony. My father had replied, “You think either of us will die soon?” My thread ceremony eventually took place in May 2001, some five years after this conversation.
You frequently come across mostly elderly relatives lamenting the fact that youngsters nowadays don’t have much interest in religion, and parents are also not doing their bit. They crib that earlier, most boys would have their threads by the time they had reached double digits, and this would ensure a more religious upbringing. However, nowadays, with thread ceremony being delayed up to the twenties, and even up to the day before the wedding (for people belonging to castes that wear the thread, the thread is a prerequisite for marriage), the elders feel that this is preventing kids from being more religious.
I’m not sure if the increase in average age has to do anything with how religious the parents are. It’s simply a consequence of higher life expectancy. If you are a boy belonging to a caste that normally wears the thread, you need to have had your thread ceremonies in order to conduct your parents’ death ceremonies. If you don’t have the thread yet at the time when one of your parents dies, some other relative has to do this thing, and you are supposed to get bad karma from this.
Hence, even fifty years ago, when average life expectancy was quite low and it was reasonably common for people to tell jai when their kids were still young, people would want to make sure that there was a good chance that their sons had a thread by the time the parents told jai. And hence, the thread ceremony would happen fairly quickly after the kid had attained the minimum age of 8.
Nowadays, with people living longer on the average, and the probability of someone dying leaving behind a young kid being fairly low, there isn’t much incentive to have the thread ceremony really early. People prefer to wait until their sons are old enough to understand the significance of the thread, the ceremony, etc.