I miss the "discussion" filter that Google used to have. For a while it still worked if you added a parameter to the URL. Now it's often difficult to impossible to search for stuff without 99% blog spam.
A defined purpose? monitization?
I suppose it would be a hard fight to get google to specifically favour non-adsensed sites.
A desire to express an opinion vs an attempt to lure you to buy something while telling you banalities about the topic.
Forums mostly see the latter as spam and evict.
Cool ads, interesting ads, but still ads.
I guess you could argue that if I google that search term I'm probably planning to buy one or something, but if I append reddit I can get a really crappy discussion tab-esque function.
If I try "Solar Powered Van" the results look a bit better but are basically the same kind of lifestyle sales content.
I think we accidentally hacked the internet into some sort of Möbius supermarket magazine aisle.