Why aren't all automobiles designed so that the Headlamps shut off automatically when the ignition key is removed?

The most common explanation for why they stay on when the ignition is shut off is that consumers want to be able to mark their vehicles' presence at night, particularly in emergency situations. Some drivers may also want to use the headlamps, on occasion, as a giant flashlight, to illuminate a dark area in front of them. Increasingly, automakers are listening to consumers' concerns on the matter. Many vehicle manufacturers are experimenting with delayed turn-off options for headlamps, allowing peopleto get out and see their way into their home at night. Others automatically turn the headlamp off. . .but leave the parking and tail lamps on to conserve the battery. Currently, certain big automakers are running experiments rolling out this feature on selected models to see if consumers prefer the change. If they do, the automatic shut-off feature will join the list of the now standard features such as automatic transmissions, power steering and brakes; radios; and air conditioning.