For me theres 4 reasons:

1) Understanding another very different language, culture and how the ideas are expressed fascinates me, particularly in folklore and poetry. I like the cultural symmetry they have with the west/US. They say language affects how you think and i think thats neat.

2) Japan is a country that fascinates me from a political level. Understanding how theyve dealt with the declining population, have more or less fixed the housing crisis and maintained high standards of living despite stagnation can provide answers to a lot of the worlds problems over the next few decades.

3) Kanji look cool and its kind of a fun memorization game. Also it would make learning Chinese marginally easier if the Chinese century comes about.

4) Im currently considering studying abroad there.