I don't think this is the answer for everybody, but for me it helps to sometimes talk about it because I didn't know at the time how to deal with my feelings. So I did unhealthy things with them. And now that for example shows by having flashbacks. I know that it happened, and that it doesn't matter anymore now. For example I was bullied in high school, I'm not in high school anymore, I don't have contact with any of these people anymore and it certainly does not affect me directly now. Yet, when I see a movie with kids walking down a hallway which just remotely looks like the one at my school, I can't stop thinking about things that happened.

Some things in your past can affect you directly right now like this. I can't do anything about flashbacks, I can just learn how to control them in some way. Other things might not show this openly, it might be that you always worry about something because something happened with your parents. If these things are bothering to you, it might be worth talking about things that have happened in the past because you can get help in processing them and not be bothered anymore.

But I don't think there's any use in talking about it just to talk about it. If you don't feel the need to talk about your childhood, then I don't think a T should insist on it. The T can't know what the issue is for you, where it comes from and so on. Even if there was trauma in childhood, some kids develop just fine, if it's not bothering you currently and on your mind a whole lot and so on, I think there's plenty of ways to have more useful sessions.