Oh neat, Google Hangouts now has Closed Captioning on Android! Personally I am rather glad my work uses Google Hangouts for meetings because the captions make things so much better since I can only lip read in person! Yay!
Lip reading is not possible in video chat because: the other person might not have their camera on, the quality of the video is generally poor, video with sound is unsynchronized, and the framerate tends to be too low.