"Pro" means you make money using it. I've personally made hundreds of dollars in the music business over the years using arrangers.
Seriously, I've had a guy in my living room all day trying to show me how great his 10-year-old synth is. My old PSR8000 was set up right beside it and everything he did I could do faster and better. Plus much more because of the styles. It blew him away.
The fact is, this seasoned pro had no idea that the arrangers can do what they do. He really didn't even know they exist.
I think in the states it is simply a matter of educating the "pros" as to the possibilities of the arrangers.
In Europe this process is much farther along, thus more dealers offer them and more sales are made. It feeds on itself.
We must stomp out ARRANGER IGNORANCE. . .
DonM