It doesn't make sense to include a separate forum for every open-source extension out there on this website. They already have multiple free discussion options available on GitHub.
They were never removed, by the way. You might find them on the DNN Corp website, but no one is really using that website anymore for community communications.
Like with everything else, things like this get forced to evolve, and not always in ways that everyone wants. Hopefully, the next phase of growth will bring with it changes that you're happier with. :)