There's an interesting illustration of this.
I have to go slightly obscure, but really you should seek it out.
There's a movie by the Canadian film director Denys Arcand
read out in English on the page, "Dennis Ar-cand," if you want to look him up.
He did a film called "Jesus of Montreal."
And many of the characters are vibrant, funny, passionate, interesting French-Canadian, French-speaking women.
There's one scene closest to the end, where they have to take a friend to an Anglophone hospital.
In the hospital, they have to speak English.
Now, they speak English but it's not their native language, they'd rather not speak English.
And they speak it more slowly, they have accents, they're not idiomatic.
Suddenly these characters that you've fallen in love with become husks of themselves, they're shadows of themselves.
To go into a culture and to only ever process people through that kind of skrim curtain is to never truly get the culture.
And so to the extent that hundreds of languages will be left,
one reason to learn them is because they are tickets to being able to participate in the culture of the people who speak them,
just by virtue of the fact that it is their code. So that's one reason.