HDMI is designed for consumer entertainment electronics. It progresses as swiftly as necessary, which is to say, not very swiftly at all. It only has to support relatively modest resolutions and refresh rates, because most consumer displays support relatively modest resolutions and refresh rates.
DisplayPort is an interface and connectivity standard designed by VESA for computers. It is the successor to DVI and is designed to support the resolutions and refresh rates we need to drive computer displays.