Donmillion you have a point but I think it just comes down to personal preference. If we were forced to use open sights I'm sure we'd all adjust and call all those scope users of the past sissies.
You're right about holding the rifle steady as the biggest limiting factor at long range shots. However in my opinion the higher power the easier it is to identify rifle shake. If your target takes up half the scope then you will see rifle shake a heck of a lot more than if it takes up only say 1/8 of the scope. Once you identify it then you can do whatever it is you need to do to correct it. Change your breathing habits, get a better rest, put the gun down and shake of your tension for a second or two. But once you correct it you know it because you can see it clearly in the scope. At worst know you can't hold it steady and you know its out of your range.
Any time yo want to test shake take a high power variable scope. Put it on the lowest power, hold it on a small target at a long range. You will feel like you are right on it, have someone adjust the scope while you're holding it to the highest power. You will then realize that you are bouncing all over and can do what you need to correct it.
However I agree that you can become deadly accurate with a 3-9 or even a 4 fixed power. Heck some old timers still use sights. Its just like driving a Cadillac compared to driving a Pinto, they both get it done. Ones just a little more comfortable.
My 2 cents.