Forums are for people with the same hobby to discuss about things they like.
This leads to more targeted acquisitions, so, more well spent money.
Ok, without the forums we wouldn't have the "devil" on our shoulder pointing to new things.
But we also get an "angel" on our other shoulder, showing us posts from people with the same taste as ours, that do not like what we want to buy.
Let alone that without the forums we would not have the opportunity to sell what we didn't like and go on with something we really like.