Hello Ganimede,
the Background is that Retail and Fashion are on the roadmap for SAP S/4HANA. For more details see the roadap (https://websmp101.sap-ag.de/roadmaps --> > Product road maps > Cross Topics > SAP S/4HANA ('S-User' is required)
There are already adaption tasks started (some technical pre-requisites) but from a functional perspective Retail / Fashion is not avalaible within SAP S/4HANA, on-premise edition 1511. Like mentioned it is on the roadmap.
Kind Regards,
Frank