For me - travelling is about stretching children (and myself when i started to do this) beyond my own world view. To be aware that Enlgish is not the only langague spoken, that differnet cultures may do things differnetly and to respect these differences and talk about them. To move beyond stereotypes of people, which generally happens nautrally when you travel and you realise not all X people are this way. To show that life is not just "one way".
And then for the sheer adventure of it - because the world and people are fabulous - i love the diversity within architecture, food, ideas, places - and also exploring nature, mountains, seas, forests, volcanoes, and views.
I hope that by taking my children on holiday abroad that they move beyond thinking in an insular way (my little place / way is the only way) - to realising that the world is a big, diverse place. That we all belong on it - it has also opened up my children to realising that not everyone in the world has access to schools, hospitals, food - and to think about this.
I am in no way saying that you can only do this by travel, reading (which for me was my option as i did not travel as a child) is another way to broaden the mind!
However i do agree that with climate change we might need to re-think some of our travelling, although the train and boats remain optoins of getting around.