Actually, there are many things that can be learn't during astral projection.
And different realms to travel.
That is also like asking- Why take a train, or why travel to different countries?
Not only is it totally liberating to leave your physical body, but you can learn many different things.
I enjoyed and learn't a lot from doing it, but unfortunely I havent been able to do it for a few months:(
But....i know this is probably a stupid question to ask but since there is different realms and dimensions does that mean that like...theres a anime dimension or a...animal dimension? And when i saw anime or animal, i mean any anime and any animal world, I.E. Dog dimension, Naruto dimension, etc.
The astral realms can hold a lot of different areas. An animal realm I could easily see happening. Something like an anime I don't see happening since the characters and the places are only a product of the authors mind(s).