Because PLAYERS don't use arranger keyboards; entertainers (which is what OMB's are) and home players (usually amateurs) do.

Yeah, there are a few exceptions, arrangers and songwriters usually, but for the most part real, honest-to-god, PLAYERS don't use arranger keyboards; at least, none that I know of, and I've been involved in the music scene on a professional level for many, many years.

chas