Or, they did write about it but it is still piled in that huge cave or stored in the vaults of the catholic church and they deemed it not worthy of being put in the bible. Who wants to hear that Jesus maybe climbed roofs and trees, maybe had bickerings with his siblings, etc? Which is why nothing is there about his childhood. Which in turn makes my point that it is not a complete book because MAN and MANS AGENDA at that particular time, decided what other men in the future would read....and disregarded the rest because they chose to be God and dictate what was said to the masses.
Just thinking out loud.
you tend to project the realities of XX century and XXI one to the everyday life of poor people in the first.
Jesus grew up among people who might have not known how to write altogether - it was Judas Iscariot who was educated among the 12 and some other wealthy friends of Jesus, but not the villagers he grew up with.
So expecting them to write memoirs - in the first century? They did not have cheap composition books and pencils -- the writing material was expensive, to write something down appropriately took time, and those people have fields and animals and work to do - they simply did not have time fore record keeping - and FOR WHAT?
they did not have books then, so the scrolls written all were in a single form, unless somebody was wealthy enough to pay for a person to make a copy, therefore if there were even some scraps of written notes from other people - chances are they simply were lost as they did not have newspapers, publishers and archives amongst them to store those.
The Gospels written by John, Mark, Matthew and Luke were all written much later and people who wrote them were not ordinary people by any measures of the time.