For home use an attached stand is OK but I don't like them for gigs. I use a Quik Lok 695 two tier stand with my BK9. I have the upper tier tilted back with a black home made shelf velcroed to it. It holds my IPad, music, notepad or whatever I need and is out of sight of the audience. Much larger than a plastic attachable music rest . Music racks and built in speakers are two things I don't like in a Pro Keyboard.
Well, production costs are nearly zero, and you can allways detach them when gigging and only use them at home... And they ahould be metal and not cheep plastic..