There's no problem running with empty stands at all. If it sounds OK to you, then it is. Filling stands with sand adds mass and damps any resonances set up in any hollow sections. You don't have to use sand. You could use small polystyrene balls or packing material. That would damp resonances without adding mass.
There are some stand designs such as the original Epos ES14 and 11 stands that are of a light open-frame design.
The main job of a stand is to provide a stable platform for the speaker to work. After that aesthetics come into play too.
The sand thing is a cheap tweak. If you don't like the effect, then it hasn't cost you an arm and a leg.