I think the gap that's missing is a lightweight, compact scope designed to fit ARs without risers or heavy mounts (like the form factor of the Vortex 3x Spitfire), with no added features like illuminated reticles or variable power. Those features have their use but not everyone needs them and they add cost and (especially) weight. For most people, "hunting scope" quality is all that's needed—waterproof and reasonably tough...like "drop it on the ground" tough, not necessarily "drop it from a helicopter" tough.