Because there's not a need, or at least there wasn't originally. Discord started out as text/voice chat for gamers; small friend groups don't need Google indexing or similar. Larger communities could likely benefit from it nowadays, I agree, but the problem is that it's not search-index-friendly content imo: How do you appropriately index chat for search? I would think this is where LLMs could be useful -- digest an entire chat group and spit out insights/answers/etc.