The developers might have their own perspectives, but regarding technical rationale for all viewing on a mobile device being in the "remote" mode, the primary ones I can think of are:
Expectation of lower bitrates on average.
Lower power CPU probably not able to handle full screen MPEG-2 decoding at 6 Mbps. Even some low end PCs struggle to keep up with this.
Plus, of course, just supporting one of the viewing modes does simplify things somewhat.
Look forward to your further analysis.