Also for people its often an embarrassment to ask certain questions, because they think its a stupid question. In a forum, everyone can see it and comeback years later (which is a good thing btw, but for some embarrassing). A chat is forgets much quicker and better.

I think asking niche questions in a forum is very helpful too, otherwise you will only find common questions. Actually the niche questions answered and maybe corrected over time is very useful in forums. Because in a chat often niche questions requires the right person to be in the right group at the right time.