There is really no reason that arranger and workstations can not be in one keyboard.
I agree that most production is still being done with a workstation because most people have not had experience with the sounds of an arranger, but that is no reason for not having the best sound engine and sequencer with the arranger function.

As usual, sounds are always subjective. I have met several persons who have the Korg Triton but still wanted my arranger for most of the sounds. Also they have said that they wished that the Triton had the arranger function so that they don’t have to go a buy another board.