We got "Right on Red" as a standard during one of the oil embargoes as a means to save fuel in the 70s.

Too many traffic light controllers are sufficiently old (as are the signals they control) to make arrows difficult, and we wouldn't want green arrows anyhow; "Right on Red" you must yield to other traffic where a "green arrow" (painted or not) would imply no conflicting maneuvers were possible (except possibly a flashing walk sign and thus people crossing in front of you).