We seem to be acquiring tags for many individual languages. While I accept it may be useful to have tags for a few highly significant languages I'm not sure we need a tag for every language.
You're right, we don't need all of them. They're around 6000 languages so... :P
Luckily the method of tag creation helps us: you can create tags only by posting questions so the system already controls what tags can be there and which ones are not needed.
A good rule of thumb to avoid thousands of tags with many dupes is to choose an existing tag and if a new one is required, it should be not too broad and not too narrow so that it can cover a reasonable range of notions.