people use it for both. if you're unplugging your HDMI Cable a lot (sharing sources, changing cables, etc) you risk damaging your HDMI Input, since they are known to be fragile. It's easy to bend pins, stress the internal circuit, etc, so the port saver gets rid of that risk.
also, the small size of the port saver reduces the stress on the input, as long as it's not hanging directly with no support. Other options for keeping stress off are things like the Gefen Locking HDMI Cable and hd ez lock, both which attach to the chassis to remove stress on the input.