Caporegime
Or just preference. I've always done it this way in Afterburner because if your fan is constantly changing, the pitch and general sound it makes will also constantly change. If it's only switching between 2 or 3 static values the change is far less annoying and noticeable IMO.
Because of the limited points it's not the same.
Also, while I can understand people having it as a preference with a proper fan set up with multiple static points, that isn't the case here as it's not an option of static or dynamic, nor is it as flexible as AB because of the lack of extra points.
Playing "The Division" at the moment is fine, as I've got the points where I want them for that game. However with something like FM19 I'd need to create a separate fan set up because it's just revving between X and Y constantly.
Either way, it's not as refined as MSI AB.