That's not the case. Today's translation and speech recognition systems are considerably larger than even the beefiest phones can sustain. There are some simple OCR models and word (not phrasal) translation systems that run on the device, but not speech recognition.
What are you basing this on? I have a nexus 5 and I just tested it. I turned on airplane mode, and used google translate with speech recognition. Can't quite tell if the translation is phrase based (looks good) and the speech recognition works well.
