now your reaching. I'm able to roll my bag pretty close to my body and navigate it quickly: left, right, in front or behind given the situation

Not at all. The fact that you do, does not mean that most people do. This is especially noticeable in very crowded terminals and only gets worse as luggage scales up.

If this is how you supplement your exercise let me just say, there are better ways.

Yeah, I go out with a packed suitcase regularly to supplement my workout. (Super sarcastic)

Also, I actually enjoy the sound of a roller bag zipping along a corrugated surface

I don't. Here's why: in certain travel situations, broadcasting that one has luggage is a distinct disadvantage, as in, it will certainly at the very least alert potential thieves that you have luggage and are a traveler. Also, traveling in cities or countries without good sidewalks or with roads that might flood regularly quickly render the wheels useless, one way or another.

As for the space saving aspect, I prefer to have a soft-sided bag with light reinforcement along the top and bottom, as the bag I mentioned does. It squishes very well, something that's harder to achieve with the traditional roller bag that tends to have a very rigid structure for the wheels to attach to.