Everyone should learn Sanskrit if only to read the great poets and dramatists in the original. The translations are often nice, but you do lose something in the process. Thanks to the incredible efforts of Pāṇini[1], the language was mostly frozen in time and is still just as understandable today as it was 2500 years ago.

I started learning it because it is India's civilizational language and I wanted to read the itihāsas in the original.

[1] https://en.wikipedia.org/wiki/P%C4%81%E1%B9%87ini