EN VAs Unknown. Why?

As everyone knows by now, most (if not all) of the characters have their VAs listed in the Chinese, Japanese and Korean dubs.

But a number of English VAs for ZZZ characters are unknown, with the VAs either being revealed later down the line or never at all.

This leads to speculation on who voices who (such as Hugo, whose VA is speculated to be the same as either Dr Ratio or Baizhu) as well as misinformation (though this tends to be debunked in time).

This begs the question: why is it that there are characters in ZZZ whose English VA is kept secret?