One widely-spoken untruth about the JLPT is how useless it is in the real world. As a blanket statement, it reminds me of how, in my 20’s, everyone told me a college degree was just a piece of paper. Of course, I later found out, everyone saying it had that piece of paper. But before we discuss it’s worth, let’s agree on a few things.
It is true that the JLPT will not guarantee you a job. It is also true that there are people who pass the JLPT who can’t speak much Japanese at all. While the expectations about having an N* under your belt may vary, I found taking the tests to have been very worthwhile.
I haven’t taken the N3, N4 or N5. But I use N2 or N1 vocabulary every day in my daily life. When I am having an especially good-Japanese-day, I even expel some JLPT N1 grammar into the world (generally of the 子供じゃあるまいし variety). N2 is very much conversational grammar, vocabulary and listening. N1 vocabulary is high-school level, as far as I am concerned. There is some grammar I may never use. But the more I read, the more I see those patterns appear.
At the beginning of your studies, survival Japanese is fine. However, at some point, you will want to learn how to express abstract concepts, to tell a complex story, to express a nuanced opinion. Or read a menu, a contract, or an adult book. Somehow you have to learn the vocabulary to do this, and the JLPT is not the only way, but it is a proven way to get there.
Everyone has a preferred way to learn, and the JLPT is a useful tool for those who enjoy the self-imposed torture and artificial deadlines of tests, like me. Regardless of how anyone learns, part of the road to fluency is seeing, hearing, and using common words. The JLPT is a ton of Japanese, deemed important by many Japanese people — it’s a good way to take advantage of a learning framework, without going the DIY route.