I think after introducing the 4800, Epson found they had a pretty good market for “people” shooters, (portrait/wedding photographers, etc). 8” and 16” rolls are directed toward that market, since the standard print sizes revolve around 8x10 “units”, as well as 16x20 enlargements.
It does seem odd they didn’t also offer a 17” version. As mentioned there are several good luster alternatives although I’m not sure which sell it in a roll version. Kodak’s inkjet luster is quite good (they created the original luster texture several decades ago, which was copied by inkjet companies to appear similar to chemical photographic prints.)