Why is it better to learn Second languages?

It has not been compulsory to study second languages in school curriculum in NZ. There is a writer who describes the NZ government’s act of making it compulsory as “finally”.

In the article, the writer strongly recommends to study second language for some reasons, especially to English native speaker. Firstly, though English language definitely succeeded in taking advantage as an international common language, there seems to have been a tendency that the other multi-lingual speakers like Singaporeans take active parts in global company. Another reason why he recommends to learn second language is that it could provide us with different kinds of ways of thinking, which may enrich our knowledge, imagination, and the other things. “Think out side the square”, “step into other people’s shoes”, and “get out of your comfort-zone”. He cites these words in the article.
This article reminded me of Japanese attitude to learning second languages. Since Japan is monolingual country as many English countries are, it seems to me that Japanese tend to think they can survive without any other languages. Even though Japan has set second language on compulsory subject, after all, it is only tool for most of students to pass entrance exams of schools or to impress themselves by showing their grades of the language such as IELTS when they find a job. This does not help them to realize the actual benefit of learning second language as I mentioned above.