Commons is where most of the media files are stored. Currently there are 18,924,867 files available and the project is advertised as "a database of freely usable media files to which anyone can contribute". When you look at the statistics for Commons, apparently the only activity that is measured is about the contribution to Commons. There is nothing about its use.
Wikidata aims to create a free knowledge base about the world that can be read and edited by humans and machines alike. At this time there are 13,538,727 items that anyone can edit. People increasingly do edit these items but it is not known how often these items are used. The statistics for Wikidata, like the Commons data are only about the production and maintenance of the project.
The point of any and all of the Wikimedia projects and the information they contain is that they are to be used. The success is dependent on their usage. The existing statistics while interesting do not measure the success of these projects where it counts. The usage. The question how do THEY use it with/without you is a most relevant question and, we do not begin to understand the use and the re-use of our data when we do not measure it, when we do not compile statistics about it.