Also, the "content" of the book of Enoch, was considered very "controversial" for its time. The book of Enoch gets into great detail about the pre-deluvian world. It literally names specific demons that "walked" the earth before the flood.
It gets into specific characteristics of these demons, even as far as "forbidden knowledge" they taught to mankind. Such things as weapon making, astrology, and even eye make-up for woman, lol.
It attempt to fill in missing years of Enochs life, like where he was when "God took him away". Its a very interesting book, along with the book of Jubilees as well. It is almost like a sci-fi/fantasy story, but written as a bible book.
I think it was just "too much", for some of the "holy" Christians back then, who had the job of deciding which books were gonna be in, or out, of the bible cannon.