Christian culture enjoys a catchy quip on a t-shirt or bumper sticker. These quips are intended to provoke and possibly shame their reader.
It’s unclear what Christian culture’s motive is for doing this, when Christ was entirely about relationship and love. It is possible the Christians think that when people see their “Hell Ain’t Cool” bumper sticker, the holy spirit will work in their hearts. By this logic the holy spirit can’t work in people’s hearts quite as well if the Christians are wearing something normal or even, heaven forbid, something halfway self-expressive or hip.
Keeping up relationships with people is a lot of work. It’s way easier to proseletyze to them from your back bumper or your chestal region.