Skeleton Horses and Horseman to spawn in the Nether

It is incredibly rare to find a skeleton horseman trap during a thunderstorm in the overworld. But what if skeleton horses and horseman can spawn in the nether? Specifically in the soul sand valley to bring the skeleton family together and to provide a land mount in the nether and an easier way to find and tame one and bring back to the overworld. How come normal skeletons can spawn in the Nether? The same principle can be applied to skeleton horses as well. Plus, it would also a challenge in the valley and a transport to move across the soul sand and soil.