It depends on what you want from biking. A well set up turbo engine is a joy to use. Loads of stonking mid range and top end, but very manageable, unlike some "conventionally" tuned engines. It's a real hoot to use, and could get you into to drag racing, which is great fun. People do these things because they can, not because they need to, and I think that's OK. And, it's different, as Michael points out. Well, that's why we do fancy paint jobs and other mods on our bikes (one reason, anyway). But it is a very expensive thing to do if you're going to do it properly, so you need to be sure it's what you really want. It's like saying, well why would anyone want a Ferrari.