People who know me well know I can become too camera-happy, taking several pictures to make sure I get one good photo. With technology, I can even record using my camera while anyone in my "film" are unaware that I am recording.
It's a matter of preservation. In this last year, I've realized how important libraries are for keeping archives, books, etc. Not to say I was ignorant, but I am at a time in my life, in whatever poetry is becoming, where the old guard is leaving and the next generation is entering.
Also, I have photos of my "growing up," but a lot of it lost.
In short, documenting is a part of saying, "These poets said this on facebook."
It also finds its own place in my work.