I think that the main reason is in the danger of disappearing. Different nations are getting influenced by another ones. They loose their individuality. For instance, in modern variants of languages we can see lots of new words which appear only in one or several countries, but do not have another analogues everywhere else. Science and technologies are developing really fast, there are several international languages which have a real impact on our culture. So, it's natural that some people are scared that the cultiral particular qualities will vanish.