Sure, I'm not arguing against ever saying why you'd do something :) I just like descriptive comments because it speeds up the business of figuring the high level structure of the code - you're right that understanding exactly what's going on can be the most difficult part, but for me that answer usually falls out as I build a mental model of what it's doing. On the other hand some algorithms need in-depth explanation that's beyond the scope of comment (hence my example of the transform).

Mind, I mostly do hobby/experimental programming, I've just been doing it for a long time. So I'm not commending this as a work practice or anything - your point about business logic made good sense.