It’s because it’s a very wooly question about questionable and subjective advantages.
If the question was “I’m going racing, will I be faster with suspension/29er/slick tyres or not?”, there’d be a good slice of decent, objective advice regarding equipment vs conditions. Along with a liberal sprinkling of bullshit, obviously.
But here, it seems there’s no concencus on where there are any demonstrable advantages, so the argument just somes down to whether people like it or not. Hardly surprising it’s all got a bit silly.