The arranger keyboard developed from the easy play features of the old home organ instruments, so are designed for the home hobby player. (Not the pro player)
While the hardware is designed by engineers, the software and layout is designed by players that know what the home hobby player wants. (The pro player is not really considered as the amount that are used out live are miniscule in comparison to the home hobby player)
Ketron is weird as they came from Solton which was more pro orientated and so tend to have features not used by home hobby players or pro players, (They try to combine the 2 which limits sales in both camps) thus people are confused as to what they stand for, even though they have some fantastic instruments with unique features. (Never miss them off your list though if you are looking for a new keyboard)

Bill