All the theory in the world will be of little use if it can't be applied. This self-admission demonstrates the complexity of maintaining a balanced tree. Indeed, the implementation they provide for B-trees goes on for almost 4 pages of code just to delete a node. The skip list takes only 20 lines of code to do the same thing. Many authors have regretted doing so when they see their code pop up in applications.
Skip lists are much simpler to implement though they are somewhat more difficult to understand.
Their simplicity creates a condition where there is only one way to insert and one way to delete a node. There is no such thing as a non-optimal solution for skip lists. Tests were run to insert N pseudo-random integers and determine the number of inserts per second for each technique. Pseudo-random numbers provide an acceptable method of avoiding this behavior. N was varied from 50,000 to 950,000 in steps of 50,000.