Deleted Comment
Too bad, when you live in a society, you have to deal with other people living in the society including those under the age of 18.
Now at the end of the day people have disposable income and have to spend it somewhere, but I don't think travel should be given the special regard that it is currently.
I'm pretty sure cause and effect run the other way. The world has changed in a lot of ways and the internet gives people a constructive outlet to fill the void.
Average number of children per household has dropped steadily over several generations. This means not only fewer siblings but fewer aunts, uncles and cousins. There are knock on effects from there that help make it less safe to play outdoors in a lot of places, family less available, etc.