1. You can't exclude people from your group if you don't have groupings.
2. The reason for the popularityof discussing the various niches differs depending on the niche. The motivation of someone constantly harping on an alleged "old school renaissance" is very different from the motivation of someone constantly harping on the one true (very exclusive) definition of "roleplaying."
3. All RPGs really are a balance between issues like playability and believability, or individual decision making versus collective action, the ability to individually control the story versus the danger that plot by committee will never go anywhere. It is useful to have labels for these different concerns. Unfortunately, too many people (too many loud people?) see these things in black and white rather than as a multi dimensional array of balanced interests. So a game that uses Rule X because it feels that Rule X is easier at the game table that Rule Y even though Rule Y is more believable gets lambasted as a boardgame. Additionally, just as a fish has difficulty perceiving water (that's probably not really true, is it?), gamers who have spent long periods of time playing a given game often cannot accurately perceive the places that game made tradeoffs, causing them to view other games where those tradeoffs are more apparent to their eyes as being adulterated in ways they do not perceive in their chosen game.
4. If I want to troll your thread, its easy to do something like pick up on your use of the word "story" or your focus on mechanical concerns rather than character concerns and proclaim that this secretly reveals some pernicious philosophical position on gaming. Its unfalsifiable, lets me attribute to you things you probably didn't intend, and allows me to turn the entire discussion into a debate on my pet issue with you operating as an unwilling stand in for an opinion you probably don't even hold. Put simply, ENWorld prohibits disrespect but permits concern trolling. These categories are a gift from the heavens to a concern troll.