There is a lot written on how android users are less data savvy that their Apple counterparts.
The actual reason for the disparity is due to the profile of the phones that carry Android.
Apple sells one model of its phone and generates the huge numbers that it does. By contrast android and its partners generate their sales through hundreds, if not thousands of models of phones. Most of the phones which they sell are low end phones which are extremely inferior in quality and performance. The android developers on the other hand are forced to produce apps which can be installed on all Android phones. Now most of the android phones cannot run too many apps. They are not designed for that kind of performance.
The poor performance of most Android devices is the reason that they are not used heavily therefore consuming much lesser data.