As has been mentioned about 1000 times, refresh rate (hz) is not the same as frames per second (fps). Refresh rate is the number of times per second the display is refreshed, this is a static value that is specific to your display hardware (nothing to do with your computers ability to provide the max refresh rate in frames per second). If you are providing less frames than the refresh rate of a device, this results in screen tearing (which is very unpleasant in vr).
This is why reprojection exists, so when the framerate drops below the refresh rate of the display the framerate gets artificially limited to 45fps and every other frame gets extrapolated from the last (essentially, half the frames are "fake"). This is why you see judder when looking at your controllers during reprojection.
Essentially, even if your computer is providing 60fps, as you say, that means (if you are using a VIVE) its getting locked to 45fps and reprojecting. If you don't notice this you probably have never played without reprojection and have a very poor baseline experience to compare to.
TL/DR: The VIVE always runs at 90hz (refresh rate) even when your computer can't provide 90fps. So you have no idea what its like to play on a device that runs at 60, 75, or even 80hz (unless you have tried one of the oculus development kits that is, that would be a fair comparison).