Originally Posted by urbanknight

You're oversimplifying it. Let's say there's sporadic parked cars all along the shoulder. It would be foolish to duck in between them for short distances because every time you pop back out to go around them, you are appearing out of thin air. Or the shoulders with drainage grates which could swallow a road bike tire. Shoulders that stop and start frequently with those deep rumble strips between them and the traffic lane (June Lake Loop is/was a wonderful example).

Iride01 's point is that there are exceptions, and you shouldn't be making blanket statements about other people's situations which you don't know all the details about.