One of the most notorious killers of pilots is the density altitude trap. Lets say a pilot in a 172 is at Columbia California, in the famous Amador county near to where gold was first discovered before the Gold Rush. Columbia is a tiny Western town with unpaved streets hardly changed since the turn of two centuries. Its near Jamestown with its railroad used in western movies and its famous saloon.
Its also a killer airport. The reason is, while only 2100 feet above sea level, it has very hot afternoons, where the hot thin air can increase the apparent aviation altitude, called the Density Altitude, to more than 10,000 feet. Thats why this tiny airport into this tiny town has a 5000 foot runway, because the DA can rapidly go beyond the ability of the planes to climb out.
I myself, while a student pilot, did my long cross country into 022, spending a few hours in town. When I went to depart, in a 152, the density altitude had climbed to 9000 feet, which means that it as if the airport elevation had climbed 7000 in two hours.
Lucky for me, I had a 5000 foot runway and a specially modified Cessna 152, called the Sparrowhawk, that had a 110hp engine and a high tech prop,
It would be easy and helpful to add DA to the displays.