A lot of people argue that we should try to protect "minority languages" and support "linguistic diversity", but I struggle to understand why having more languages is actually a good thing.

I would be very interested to hear about concrete benefits in the present to linguistic diversity.

Lots of random musings I had on this

A lot of people say things like "it helps you to think differently" which I have not really understood at all (I speak multiple languages, for context, some quite different), but my sample size is really just me in saying that. They also say things like "protect minority culture" which I think is quite harmful. For example my great-grandmother immigrated to an English-speaking country in the west from Africa (she was Indian-African), and she could not speak a word of English which put her at a massive disadvantage, but also gave other family members a lot more power in their relationship because they could all speak English. [Edit: I think there's a gender aspect where women are expected to maintain the traditional language and the burden is not put on men in the same way]. I get the whole assimilation versus integration, but I think there's a very strong case for trying to assimilate (into the dominant group).

I have yet to see a case arguing why it is better to have more languages (and thus necessarily less mutual comprehension and a more segregated world) rather than a single one (e.g. if everyone spoke English). My issue is not really with high-level philosophy about what would be better in an ideal world, but multilingualism as a practical concern. For example, Tildes does not really seem to 'believe' in multilingualism because it only allows English (which personally I think is better than if we had people arguing backwards and forwards in many different languages, but I am also a native English speaker so that might prejudice my perspective).

Most of the arguments about this that I see are from (usually) French speakers bemoaning the decline of their language (and it's kind of ironic to see France becoming a flag-bearer for linguistic diversity given that they exterminated a lot of languages to force French upon the world).