How is going into turn-based mode and not taking your turn any different from a full fledged pause?
Lots of ways.
The full game world doesn't stop when entering TB mode, so NPCs can still patrol and possibly find you.
Sometimes you
can't go into turn-based mode (e.g, for a few seconds after exiting TB mode)
Pausing during a cutscene would be great.
A full-game pause would likely pause everyone in MP, while going into TB mode only affects nearby allies.
...probably more I can't think of right now.
