Swampy's right on point. This rig was specifically designed to be easily worn under a cover garment in an SHTF, urban environment.
Imagine SHTF is underway, but you are still able and needing to travel into town for supplies. You obviously don't want to be in full kit walking down the streets, so you put on the U.P. Rig under a light jacket, or even hoody - and roll into town, unnoticed and inconspicuous. Keep your rifle stowed between the seat and the console or somewhere easily accessible but out of sight.
Mosby described a similar scenario, and this rig is absolutely perfect for what it is designed to be used for.