Perhaps the old reasons will do just as well. Hokkien is an interesting case of being involved in a potentially fractious political situation- one can imagine to further distinguish themselves from the Chinese mainland, the people of Taiwan promote the use of Hokkien. Not dissimilar to say bilingual laws in Canada.

After all, the nineteenth century saw the consolidation of national languages and elimination of regional dialects in the name of fostering nationalism, which continued in the twentieth but also saw the revival of languages like Irish or Hebrew for new nationalisms.

I doubt that desire for cultural differentiation is going to change much about the diglossic situation in Taiwan, since the continued use of Traditional Chinese characters is already a pretty big differentiator. The government is making some effort to promote the Tai-lô writing system (e.g. https://tailo.moe.edu.tw/index.php ), but overall there's very little incentive for Hokkien speakers to become literate in it. If you look at Wikipedia visits from Taiwan, 92% go to the Mandarin version, 6% to English, 1% to Japanese, and Hokkien is in the tail of small languages behind even Cantonese and Classical Chinese. Of these, I think English is most likely to grow in the future.

Also, the differentiation potential is somewhat limited due to the fact that the majority of Hokkien speakers lives in Fujian province on the mainland (Hokkien = Fujian) and there's some preservation work going on there as well. E.g. Xiamen University's Speech Lab had a working demo of spoken-Hokkien-to-written-Mandarin translation in 2018, although the link shortener they used has since suffered from link rot. https://speech.xmu.edu.cn/2018/1215/c18169a359542/page.htm

You’re not wrong, not to mention the problematic nature of conflating Hokkien with “Taiwanese” identity, as that then omits the Hakka, never mind the aboriginal languages. But one could see a Benshengren revival of Taigi nonetheless, even if only as a set of quixotic pan-Green government initiatives.

Also, Hokkien interest is present even outside of that geopolitical flashpoint:

https://www.todayonline.com/singapore/stories-behind-tiktok-...

Preservation of a cosmovision and a form of intelligence, not just a language. Furthermore, I hypothesise whether kids lose intelligence when adults shut their mother tongues off.

We're making the opposite choice, my wife speaks Cantonese to our kid because we believe it's worth preserving (of course, the fact that there are a lot more medias in Cantonese than in Hokkien makes it easier to preserve).

Of course Mandarin, is more "useful" in a purely pragmatic way but languages are social things, they're tied to culture, they help create relationships with other people who speak those languages (I have plenty of Teo Chew friends who have made very good friends with others from different country because they are kakinang) and speaking multiple languages is always worth keeping.

Plus even besides this, having a multilingual home, regardless of the usefulness of the languages that are spoken, is associated with a lot of cognitive benefits for children so the thousands of hours learning a different language are useful.

I like that we're preserving dying languages by maintaining the ability to understand and translate them as archives of humanity on Earth's past, but I'm hoping in the next century or two language attrition will whittle all the world's languages down to just a handful.

The day every person on Earth speaks some shared common language (ideally one so straightforward that it can be learned by children within a year or so) will be a day I'd celebrate as a monumental milestone in the development of our species.

It's fine if people know other languages too, but having that shared global one is vital.

I'm happy to lose innumerable untranslatable phrases and cultural understandings in service of this.

I disagree. There is no possible benefit to a monoculture of language that would justify the immense loss of culture and of different ways to see the world.

Cultural spheres have always managed to come up with a lingua franca that enabled them to exchange ideas. English fills that role currently and will probably endure to dominate. Even if something goes monumentally wrong with the Anglosphere, it will endure until another language manages to step up to that role.

Children are perfectly able to learn multiple languages within a few years by pure immersion. I can't see what further optimization here would achieve.

Still, judging by the events of the past, languages that are not sanctioned by some state will probably all die out by the end of this century. Further erosion is very unlikely though. The language of any country with at least, say, 50 millions speakers is probably safe.