As always I would add profits come into play for manufacturers. merging an arranger and workstation synth together negates two separate profit incomes and two separate sides that use them individually.
Then there is the "CASIO" thought effect that will never go away in the minds of potential buyers and players as that an arranger is nothing more then a cheap Casio you see in a big box store that sounds like a toy for example your playing on stage with
a TOTL arranger, Genos, Pa4x etc,....
and some lady comes up and says to you ..
"Oh that a nice piano my grandson has one just like it" or
"Hey I saw them in Cosco on sale for $99.00 and I have a
coupon for one.
I think Bill nailed it on arrangers with the HOME KEYBOARD/OLD ORGAN mentality still lingering in the minds of many people. I hope one day it will change...sadly we probably won\t be around to see that.