The reasons thinking traces are pretty much gone is, supposedly, to prevent distillation. Whether that is actually true or just an excuse is up in the air (because I at least am not going to trust Anthropics claims on why they do it).
And because the thinking, which does makes it better at achieving outcomes, contains naughty words and information (e.g. private information). https://stolen-thoughts.com/
And because the thinking, which does makes it better at achieving outcomes, contains naughty words and information (e.g. private information). https://stolen-thoughts.com/