Torrent clients are widely available for android.
iPhones attractive a different sort of user who would probably prefer to keep paying .
Torrent clients are readily available in the Android app store (not sure about Apple), and web browsers can still get to any websites. Since the resulting download is DRM free, it can be viewed with standard video players.
Nowadays it would be rather difficult to install a piracy app on your phone (not impossible, but definitely harder than simply downloading a binary from sourceforge). So you're left wish shady streaming sites who in my experience have terrible usability.