All modern receptacles have places for additional hot/neutral wires so you can add more outlets in series, but they all have a single screw or hole for the ground wire.
Why don't they have two ground holes?!? I see many receptacles wired where the installer simply twisted the wires by hand, or only used electrical tape, or used a wire nut but did not use the proper size, or did not know how to properly use a wirenut (only doing a single twist)! Sometimes the connection is good when they install it, but since there is so little space behind a GFCI for example, they had to manhandle the wires back into the box, and this caused their halfass attempt at a connection to come loose the second I pull it out of the box.
I am so tired of replacing receptacles only to find that the previous installer didn't know how to continue the ground line properly.
It would seem that adding a second hole would be preferable to the dangerous situation that arises when someone does not have/know how to use a wirenut correctly.
Is there any good reason they make them this way?