Because that's what He was supposed to do, culturally. He also was learning his trade, carpentry. Those take time. Yes, He is God, but he lived as human fully, too.

It's actually amusing because in several accounts I've read of people who have interacted directly with evil spiritual forces, they deride Jesus by calling Him "The Carpenter." (They refuse to say His name or most other titles ascribed to Him.)

So, I don't really find the story jump all that disturbing, though it would be interesting to know more about His younger years, though, the possibility remains strong that it was so boring or typical to most that it just wasn't bothered to be written, like so much else that the writers, especially of the OT, assumed their audience knew.

Also, of course Jesus knew parts of the book of Enoch. There were probably few Israelites at the time that didn't. The fact that it was preserved so well in the dead sea scroll caches is testament to that.

I'm very curious as to if there is any scholarship on the wisdom books of The East having made the long and complicated trip to the Near East or other parts of the Roman Empire and were also translated to local languages. That's not something I've ever heard, but that's not very surprising since I've never thought about checking that out.