Running a tach now is just 50 cents worth of a computer output d/a spot, a moving needle, and a designer to put it somewhere. Why they don't put it in a marquis? Probably the 90 year old ladies not wearing their glasses would see "20" and think they were going a lot slower. (j/k, but their study groups probably found tachs intimidating or confusing-- these same people put in the fake oil pressure "gauge" in ford trucks)
offtopic, but back in the day they used to lock out 1st gear on the automatics b/c cops would get excited and slam the shifter down to 2nd for a manual kickdown. Bet this is done electronically now.