Oh, right. Those. It's less of an anti-esthetic for the Rebels, I think, because their transports blend right in with their more diverse-looking fleet. We see all those transports with the Rebel fleet during the battle of Endor. Those Sentinel shuttle things just look unsightly in an Imperial fleet, for whatever reason. Probably because an Imperial fleet evokes that crisp, fascist, uniform vibe. Look at their massive, wedge-shaped capital ships. Even their support ships like Tartans, Lancers, Carracks, all maintain the same precise look. Hense my compelling need to omit them! At least for the Imps!!