Last modified: 2014-11-17 21:32:10 UTC
...because no upload will happen if you tap on them. Mobile web has already switched to a more neutral placeholder: https://bits.wikimedia.org/static-current/extensions/MobileFrontend/less/images/noimage.png - makes sense to do the same in apps too.
patch for Android: https://gerrit.wikimedia.org/r/173950