Bear-baiting and slavery also were 'popular with constituents' in their times . . . that doesn't seem to have been a very good argument for keeping them around.

Sorry, are you wearing blinders? Most cultures don't disappear simply because "no one chooses to adhere to it." Most cultures are actively destroyed or consumed by larger, more aggressive cultures. English-only laws are but one of many examples to be seen in the USA. On the other hand, active preservation of languages and their related cultures can offer great value for a current dominant language and culture -- both inherently, and for some potentially unforeseen future crisis. (Or were you not aware that, If not for the Navajo 'Windtalkers', we might all be speaking German.)