Someone said ideas?
Endermen are both scouts and naturally attracted to dimension cracks. Ender Pearls soak up this energy like a Russian in a room full of Vodka. Enough Enderpearls, fully charged up can essentially plug holes right in the skin of the Universe.
It could be that originally, the End was a beautiful place until the Enderdragon came, and his ability to convert matter into energy and said energy bleeding into the Endermen forced them into their current, twisted shape. They also developed similar features as the Enderdragon. (Perhaps they were imprinted with his DNA?)
ORRR
I'd like it if Endermen were really trying to absorb the Dimensional energy to heal/help.
Maybe the End is some sort of Dimensional Limbo.
Tossin' ideas round like it ain't no thang.