Why alternate tune?

There are many reasons to tune your guitar differently, some of the most popular are;

Achieving a new sound
Forcing yourself to grow as an artist
Adapting to a new style of playing
Differentiating yourself from other players
Writing songs
Playing slide guitar
To cover a song written in another tuning.

So have fun, go experiment.

(also, Syd Barret of pink flloyd, being so twaked out at a show he detuned all his strings to lord knows what and hit it making an awful sound. The audience went wild! *not recommended*)