This is due to stochastic learning on a per-example basis where a weight update on a misclassified example may apply only to a small fraction of data that have been seen before.
instantiating SGD to the following stochastic subgradient leads to the perceptron algorithm for pairwise ranking 3 (Shen and Joshi, 2005): Our baseline algorithm 1 (SDG) scales pairwise ranking to large scale scenarios.