I need some reasons...

[Nurumaiel]

Why, my dear, if you want to learn it and enjoy learning it and it is not harming you in any way, isn't that reason enough?

I attempted learning Elvish at one point, and though I never came along too far, it gave me a good first grasp of exactly how a language worked, as Tolkien did construct it as a real language. Consequently when I began learning Latin, and one or two other languages, I had an idea of what I was doing, however vague, and furthermore I had already worked out, through studying the Elvish languages, a study method that was best for me.

And so it very well can be useful for something.

Nobody has ever asked me why I eat ice cream. Isn't it a waste of time to eat ice cream? Why, what is it useful for? Sure, fruit is a very useful and healthy thing to eat, but ice cream, now. If anyone ever asked me why I eat ice cream, I should reply: "Why... because I like to eat it. It's enjoyable."

Now, Latin has many ways of being useful (and, as I mentioned before, Elvish has some ways, as well), like fruit, so why learn Elvish? "Why... because I like to elarn it. It's enjoyable."