Simplicity is key. Years ago I set up a woman with a small OverCamp. She was really excited about it and had done a ton of research. Turns out it was a really poor choice because she was 5 foot 2 inch tall and had a lifted Explorer. She physically couldn't open the tent. A small Columbus was perfect for her because of the ease of opening and closing, so the added cost was justified.
Let's look at the OverCamp in detail, it is a good example of design compromise. It does work well, and is a good solution if you want to load kayaks or bicycles with you up on the racks. The limitations stem from its heritage, it was designed as an expedition tent. It is designed rugged and to be easy to repair in the field. The frame and ladder for example are made of steel, cheap and easy to repair and modify, but heavy. The ridgepoles are also steel, but if you break one, you can repair easily with parts from a plumbing store. The deck is multiply, a very high density plywood that is sheathed with a laminate for easy cleaning. Again, very heavy but dimensionally stable, strong and adds good insulation ability. The result is that a US spec small OverCamp is something like 120 pounds, very heavy and a pain to get off and on your truck.
If you want to make a nice light OverCamp, you would start with an alloy frame and ladder, a composite foam cored deck and nice light fiberglass ridgepoles and high tech tent fabric. Add light inflatable mattress pads and the whole package would be half the weight and be just as functional, maybe more. It would hold up well on a passenger car but last about ten minutes if you mountedt it on an offroad trailer on dirt roads. So the designers have to spec the tent to the higher weight and durability knowing that someone will use it off road.
I think as the concept of RTT gets more traction there will be more niche tents. AutoHome for example has gone from something like three tent designs 20 years ago to like 30 now. I think the new carbon fiber tents are an attempt to shed the weight but still keep the comfort and durability.
Rich