The board on a server is a bare bone design, where many common features are removed (as they are not considered needed). Examples of such are monitor ports and multiple expansion slots. Clever workaround designs are made to leave out components without loosing functionality or adding of costs. A power supply? There is no power supply on an OCP server, as it gets powered through a direct interface (from a power bar on the rack). A front bezel on a server usually fits no functional purpose, it actually limits the airflow through the server – therefor you won’t find it on an open compute server design.
All in all, the open compute’s vanity free design takes away on average 6lbs of unnecessary hardware on a server.