I think official forums just help to centralize the community. If we didn't have these forums, I assume that many of us would just end up picking our preferred fan site and using their forums. It also provides the community team with a way to distribute information and answer questions without either having to coordinate with multiple fan sites, or having to post a whole news post on the main site just to address relatively minor bits of information.
TLDR: The forums are a great tool to collect feedback and distribute information. While many posts are rather useless, I like being able to get direct feedback from the community team in an official context.