I agree, many brands out there do hollow out gold cases and bracelets. Some are more subtle than others.
In Bvlgari's case, I guess there is an argument that they do this for weight and balance reasons, but the thing that annoys me is that certain marketing shots (even on their website) show the back of the gold bracelet to be solid - or, at the very least, not scooped out like it is in the metal. That's what gets me and I have no idea why they do this. If they believe scooping it out is for comfort reasons, then they should stand behind this and show the bracelet as it actually is, and not an idealised version of how it "might" be.