I’m sure there are many different motivations.
Some people study Japanese because they love anime and manga. That is not why I study Japanese.
Some people study Japanese because they want to go to Japan. That is not why I study Japanese.
Some people study Japanese because they love the culture. That is not why I study Japanese.
Some people study Japanese because they want to find a Japanese partner. This is not why I study Japanese.
Some people study Japanese because it’s difficult. This is not why I study Japanese, though it’s getting closer.
Why do I study Japanese?
Because I’m bored. Seriously.
I picked one of the most difficult languages in human history to study because I had nothing better to do.
That is me, in a nutshell.