This is absolutely not true. Perhaps you are not choosing the right time to sit down and comment. I'll usually put in quick comments as a module is under cons

This is absolutely not true. Perhaps you are not choosing the right time to sit down and comment. I'll usually put in quick comments as a module is under construction. Once it reaches stability (meaning, I am moving on to something else) the detailed comments go in. Also, if we are talking about embedded there are a lot of comments that are invariant because they might explain details of the hardware interface this particular chunk-o-code might be dealing with. That hardware --external to the chip you are programming-- will not change unless a hardware revision is done, which is far less frequent than code iterations.