Just because you don't see the benefit of the language and culture of a distinct region being maintained by its own people, doesn't mean there isn't any.
The world would certainly be worse off if we lost all the diversity in it because people only see things in terms of investment/gain but are blind to the richness of allowing people to maintain their heritage.
Besides which the only part of the article that mentions taxes is when aomeone mentioned Andorra being an independent nation and paying less taxes to be autonomous than the people of Val d'Aran pay to Spain. Additionally Catalonia, where they speak Catalan, has been trying to separate from Spain. If anything, these languages are not in "life support" at the cost of all the citizens of the nation, they are actually paying more taxes due to being a part of said nation and have all the right to keep their language- especially so given the history of the region when it comes to their treatment by "the country as a whole".