Yes, Kingfrog... I believe all but the self-taught 'home' arranger player has FAR more important things to do with their LH than slavishly play the damn chords all the time...
Doesn't stop me from using an arranger in preference to any other kind of keyboard, though, because in the ONE keyboard, you get all the rest thrown in. Most arrangers play sequences well, some play MP3's, and they have a live interface FAR better than WS's. Yet most of the capabilities (other than arp and loop stuff, which is only good for more contemporary musics).
I have LONG preferred plastic 76's as a size and action choice, because of the need to play both organ and piano from the same keyboard, and had several WS's in this size (still have a couple, actually!).
But a WS is kind of screwed when asked to do something you haven't already programmed in. In fact, you can't even get a drum machine with the kind of flexibility that a TOTL arranger has. The best of them merely link two patterns and maybe two fills. An arranger's drum section can have four patterns, seven fills, four Intros, four endings, breaks, you name it.
In fact, why HASN'T anyone made a drum machine this capable?

To be honest, other than modern beats, an arranger beats a WS hands down even at the things it is SUPPOSED to do. I certainly have never had to explain my use of an arranger in the studio or on 'call' gigs. I simply turn it on, start to play, and watch them smile! Drummer shows up late, no problem. Rhythm section shows up late, no problem. EVERYONE shows up late, no problem...

Can't really say that about a WS....