Well it depends on whether your T focuses a lot on the past or not, and it depends on the issues you bring to therapy. My T has a here-and-now behavioral approach for the most part, so we didn't start with examining the past. My T and I just started getting into trauma work (6 months after I started therapy), when before we were dealing with my values, dealing with social situations, exposure to different things that scare me, how to deal with my sisters when things get crazy, etc.
She's only working on the trauma with me
because it's so hard to talk about -- and so many things are a DIRECT result of CSA -- so, here-and-now, I need to talk about the trauma so I can talk about sex at all (right now, I cannot even have a conversation about sex with somebody -- or buy tampons at the store, or condoms -- or say words that have anything to do with sex out loud). In her opinion, it would be useless and retraumatizing to me to talk about the past if it weren't so DIRECTLY affecting the present. And I agree with her. Why should I talk about what hurts if it won't help me to do that? But, it will help me, so I'm doing it.
At the clinic where I work, they never do trauma work at ALL. They deal with people with OCD and do exposure and response prevention, mostly, and they don't think talking about the past is any good unless you have PTSD. But I'm not sure I agree with that approach, necessarily. I think it's about what your client thinks will be helpful, too. So if my future clients think talking about the past will be helpful, when I'm a therapist, I will not question that, even though I plan to take a mostly-behavioral approach.