On the "Questions" page of each Stack Exchange site, there are links at the top to sort the questions by "newest", "frequent", "votes", "active", and "unanswered".
At least that is what it looks like if I am logged in. If I am on a site that I don't have an account for, or if I am not logged in, the only one I see is "newest".
This seems to have been done recently. I could swear I saw the other links, even when I was not logged in, until a few weeks ago, or maybe later than that.
Why was this change made?