I have to agree with Alex. If everything gets said in chat, none of that information ends up posted in the topics. Even if we saved chat logs, it would be a nightmare sorting through who said what to whom about which deck and then indexing all of that for people to find in searches.
Topics are better for organization, so when the next wave of n00bz come crashing on our shores, asking about a particular deck, they need only look in one place, not dozens.