For professionals Diki is correct, (Hence workstations are so popular) however the Arranger keyboard has always been designed for the home player (There a cheaper spin off of the home organ) which probably account for about 95% of the sales of arrangers, and as most home players aren’t interested in midi or linking things together, (Apart from adding a slave keyboard and pedals to make it like a portable organ) therefore there is zero incentive for arranger manufactures to agree on a common style communication method a sales increase would be minimal.

Bill