Musing i think only prefer English language because till now i have not seen the answers or question in other any language and we may see this feature in future soon.
Musing may not understand other language and other people who need answers to their question in other language may not even understand your language so i think writing answers and question in other language is not worthy for many users.
English is a very common language so this mite be the known language for every people and may even not think to read answers in other language which is not their native one.
This will be lack of upvotes if the post is written in other language and this may decrease the users if people see other language it they do not understand