One of the biggest problems with crypto-currencies is that they aren't tangible. You can't see them laying there. You can't go through your couch cushions to see if any fell out of your wallet.

If you don't remember you had them, and as you get more coins and more wallets, then they just fall into the memory hole.

I know this will be solved in the near future. (near meaning decades)
And, I am glad your son is already into cryptos. It will make his life much easier as all of us shift over.