That’s because you are not following the industry; denied-GNSS navigation has been a thing for a while. I have also seen several drone designs that can attach t

That’s because you are not following the industry; denied-GNSS navigation has been a thing for a while. I have also seen several drone designs that can attach themselves to the silo steel wall from the inside for inspection jobs. UAVs aren’t perfect; their biggest drawback is the battery endurance before jumping to an airplane scale, but they are effective, efficient, and reliable for all their applications, even more than UGVs (UGVs have been used in real-life applications since the 90s or even before, yet drones took over in the last decade). QUGVs, on the other hand, are merely a toy, for education, or marketing purposes. The only purpose I can see for QUGVs, or even UGVs in the future, is interoperability with drones, but definitely, drones are and will be the dominant force in the field for the future.