When pop-up headlights were conceived, the DOT allowed for the use of just 7- or 5-3/4-inch sealed beam headlights. This was great for parts stores because only a few part numbers could cover every car on the road. The regulations controlled how high and how far apart they could be mounted. The solution for designers was pop-up headlights.
Where the designers created beauty, the engineering department created pain for technicians who had to fix them. Vacuum-powered servos were always the farthest vacuum-powered components from the engine and were prone to leaks even on new cars. Electric motors would burn out, strip plastic gears or break linkages.
It is difficult to pin down the exact reason why pop-up headlights died. Some say it was in 1984 when the DOT allowed Ford to use composite headlights and not the mandated sealed beams on the 1984 Lincoln Mark VII. Some say it was European pedestrian safety laws. But, whatever the reason, the 2004 Lotus Esprit was the last mass-produced vehicle to have pop-up headlights.