IRC simply a different use case than a forum. I think both are useful and I don’t see a reason why a company couldn’t have IRC and a forum, there’s no contradiction and the overlap is small.
Forum are very useful for example for use cases where the topic is extremely specific and you throw out a post “who else does this and have this issue?” and hope someone will find your post through internet search and the more people find the thread the higher the likeliness to find a solution.
IRC is nice for quick back-and-forth type conversation for topics which are more “common”, where the requirements to participate in teh conversation are lower. For example, a discussion on a potential feature request.
Oh no IRC and a forum are near perfect complements. Discord and friends try to integrate the two functionalities, but I've yet to see that work even remotely well.
Except that newer products like Slack and email providers with their conversation view are conflating the two use cases.
Slack tries to implement features of a forum by allowing threaded conversations. Conversation view email removes the nested threads and makes the email thread look more like a chat as opposed to a forum discussion with multiple threads.
Forum are very useful for example for use cases where the topic is extremely specific and you throw out a post “who else does this and have this issue?” and hope someone will find your post through internet search and the more people find the thread the higher the likeliness to find a solution.
IRC is nice for quick back-and-forth type conversation for topics which are more “common”, where the requirements to participate in teh conversation are lower. For example, a discussion on a potential feature request.