tenses

A writing question for those literary folk out there:

I frequently find myself writing in the present tense when writing fiction. As in, "She walks up the stairs and turns left" instead of "She walked up the stairs and turned left." I see very few published works with this sort of tense structure. My questions are 1) Why? and 2) Does anyone else do this? It seems to come more naturally for me than writing in past tense, and yet, when I'm done with a piece, I usually go back and switch it into past tense simply because that's what I'm so used to reading. Is there an official ruling on this from the Writing Illuminati or whatever? I seem to remember hearing that writing like this is A Bad Thing and The Sign of an Amateur, but... well... I like it.

(Note: capitals denote an official tone, from someone who apparently matters.)

Not that I think I'll change how I write because of an answer one way or another. Just curious.