Not necessarily, we could use an existing server as well. Some servers offer a way to use our own DNS with their infrastructure so our channels could have addresses ending in @chat.haiku-os.org and we could still have someone else taking care of the hosting (ideally we would give them a small amount of money in return, I guess? or hope they find a sponsor, as Freenode does for IRC)
It is not difficult if you know it. But imagine you never used IRC before and you want to join the Haiku chat. If you just connect and there is no context, you just get an empty window saying “you have joined #haiku”. If you don’t say hi or something like that, it looks like nothing is happening.
On the other hand, imagine that when you connect, you get about one page of the recent discussions directly in your client. Now, you immediately can see if the channel is active or not, and what kind of things people are talking about. So it becomes clearer how the channel operates and what is going on.
This is a small difference, but I think it has big consequences for people joining for the first time. And it will help them stay around.