Well, here's the thing: "backing" is considered antithetical to proper framing, for the most part. That may be less of a concern with digital prints (no matter the medium), since those prints can easily be recreated as necessary, but full-surface mounting to a rigid substrate is not a reversible process; once it's done, it's done. And while that may be good enough for most people most of the time (for decorative applications or commercial display) it's not something that anyone who is selling into the "fine art" world would touch with a ten-foot (or three-metre) pole. Conservationally-sound framing (with reversible hinges, etc.) is fiddly, time-consuming stuff and requires a lot of horizontal storage space for drying, etc., between stages. And you'd have to deal with expensive and easy-to-break museum glass if you offer glossy prints. Since the market is largely dry-mount or frame, and framing is the fiddly, expensive and (relatively) low-margin part of the trade, that's the easier option to drop.
There's a fascinating amount of detail here that the home/prosumer photographer is unaware of. There's also an impressive amount of manual work. I'm not sure, but that kind of sounds like a startup opportunity to me.
