My understanding is that it's because the entire blockchain would need to be stored on the device which from even a data perspective is too much for a phone. Th

My understanding is that it's because the entire blockchain would need to be stored on the device which from even a data perspective is too much for a phone. The processing of data on the chain will also be too computationally difficult/expensive for the phone. You would either run out of battery immediately or the phone would crash.