I fully agree with you Ian..
A lot of the stuff is already done in arrangers to sound good right out of the box. And the arranger keyboards have more SA, SA2, SN & DNC quality voices as compared to synths/workstations. And no matter how much editing is possible on a synth/workstation to sound great.. it definitely lacks the instant gratification of arranger playing
And also the creative possibilities of trying different styles to play the same song is a breeze in arranger keyboards.