‘In his foreword to the 1967 edition of the book, C. P. Snow describes the Apology as "a passionate lament for creative powers that used to be and that will never come again".’
Well it is obvious that the father does this when his son is a 20 yo. And it is obvious that this is a clever hint. My point is why not to do this when his son is 10 yo?
Probably because the father was only just 30 when his son had turned 10 and hadn't realised yet that he had already lost 3 stones.
That said I feel I still have plenty to share with my children and now grand children - each day is a gift and each one will have mundane tasks, challenges and triumphs that all need to be dealt with accordingly.
Maybe at ten the child would be able to understand the words, but do you really learn the lesson when they have not yet spent a decade of being a teenager that is now over?
I didn't gather that from the comment, and tend to agree with the other reply. 20 is probably the earliest that someone would grasp an idea like that, and maybe >40 would be a good time to have realized it yourself.
At age 10 you're still truly a child, you don't know shit about shit. Age 20, you still probably don't know shit about shit, but you might
20 years old is too late to start any personal development, try this approach with stones to 10 years old instead.
50 years old is a final point due to "A Mathematician's Apology" by Hardy.