The reason for it being in 
is simply for thematic reason (The flow of energy from creature to opponent). I may change it to other elements if I can come up with a new theme.
I've been thinking about a time version of this concept, actually. Damage to your opponent wouldn't fit the theme there, but it would fit the same gist of something that "resets" the target creature. Essentially, treat it as though that creature was just reverse timed, then played again, so any status effects would be removed, and the creature's stats/abilities would be reset to their base amounts. Good for undoing negative things on your own creatures, as well as undoing any growth or positive spells on opponent creatures.
Water lends itself to some kind of purify-based theme. Purging the target creature of any statuses (and maybe generating
for each one you purge). Life or light also similarly fit that type of theme. Entropy might be able to pull off a funny version where you replace each status effect on a creature with a random other status effect. That probably wouldn't be useful, but it would be funny as heck. Maybe an entropy version, to be useful, would have to affect every creature on the field.
So anyway, there are ways to morph the concept to fit other elements.
