Do you know Chinese carbon tubular rims ?

Tubular rims are most commonly used in competitive road and cross-country races.
The thread and casing of the tubular tires are molded or sewn around the inner tube.  Then gluing the tire to a carbon tubular rim. Which lacks the rim wall needed to secure the bead of the open tire.  More professional riders prefer the Road tubular rims. Because they are lighter, softer and the rolling resistance is lower.

What is the advantage of the Bicycle carbon tubular rims?

Tubular are becoming more and more popular among the competitive cyclo-cross racing. Because they can resistant more flattening than the clincher type. Besides, they allow much lower tire pressure for maximum traction and comfort !
Now the tubular rims most used 25mm and 28mm width. Wider rims are better for handling on corners, crosswind condition. U shape tubular rims have better aerodynamic.They are super lightweight but in high stiffness. It is really great choose for climbing and cyclo-cross.

Why riders not like light carbon tubular rims on training?

To most riders, the tubular type rims are not ideal for the training or recreational riding. Because if it puncture, it will be hard to repair. Gluing the tubular tires may be not too difficult in your workshop. But it is an intimidating and messy task for the amateur riders. Most riders will use have one set of the clincher or tubeless wheelset day by day,and use their tubular rim only for racing time.