There are many reasons for secrecy.

Showing that you know how to keep a secret shows that you’re trustworthy.

There are also certain rites of passage that are more striking if you don’t know what to expect (but it’s always benevolent).

Also, as it’s a place where speech is totally free, it makes it easier to open up. For example, if we’re having a discussion about LGBTQIA+ rights, I can share my experiences as a bi person to enrich the discussion, and I don’t have to worry about being outed.

Finally, in Europe, the memory of Nazi persecution is still vivid, and today’s far right hates us too. Secrecy, or at least discretion, is a protection.

But I have to admit that it raises suspicions and feeds conspiracy theories. So secrecy has its downside