Understanding something intellectually is not quite the same as appreciating it viscerally because you have done something similar.

I guess, but kids still go outside and do chores. What do you think kids no longer do that kids in Twain's novels did?

They certainly don't use many of the same words, probably don't sail or float on a river (but how many kids could ever do that). What else? The core elements of friendship, loyalty, cunning, and the base satire are all still relevant and visceral today