Weight is so important in HMDs that it is sometimes overlooked. Lower weight means greater comfort. It means the ability to wear the HMD for longer amounts of time. It means that you can almost forget you are wearing it. Balance (as opposed to front-heavy) is also important as it impacts neck strain. Sometimes, HMD vendors add a counter weight in the back to balance their front-heavy design, but that's clearly the wrong solution.
Why do professional HMDs have to be heavy? The traditional thinking is that this is like asking why a manned fighter jet has to be heavier than an unmanned plane (e.g. drone or UAV). The pilot and flight suit add about 100 Kg to the jet, but that's just the beginning. Now you need oxygen, and a seat that you can eject, and instrumentation you can read. Before you know it, you need larger engines to carry this weight and longer wings and more fuel, so the net difference is much larger than the weight of the pilot.
Traditionally, that has been the thought of professional HMD vendors. The idea was that if you want wider field of view, you need a large lens, and to minimize distortion it needs to be complex and heavy. If you needed high resolution, you had to use more expensive display elements that needed external lighting (and a way to diffuse the light so that it is even). Before you know it, professional started equating with heavy. Heavier designs meant larger (and yes, heavier) head mounts.
And not true. At least not for long. By using new types of displays, optics and components, professional is no longer heavy. New products, such as the xSight weight about 10-12 ounces. Not quite as light as some of the consumer HMDs in the 'Skymall magazine', but getting there.
So will this be the year of the 'good enough' professional HMD that combines wide field of view, high definition and light weight? I hope so, and I think it will.