Users don't necessarily wanna join or know how to join a discord server/forum just cuz they're using a particular software/product and need help from time to time.
An alternative to Taku would be forums hosted by the official group/co. in-charged of the product. These are a hit or miss. They usually require a sign up as well.. so now users need one account per good or service. (On Taku, a user could have a single account that spans across products).
Also, nothing stopping Taku from offering different kinds of chatting services in a single solution: Forum, Q&A, instant chat.
I suspect a selling point would be increased user engagement in terms of helping other users out... in the past, as a user I might come across a question on a forum i kinda an help out but I'd be too lazy to create an account just to post.