Why are there no plants on Mount Everest?

This statement isn't entirely accurate. There are some plants that can be found on Mount Everest, although their diversity decreases significantly at higher altitudes. For example, there is a moss species called Bryum argenteum that has been discovered at an altitude of around 6,500 meters. Similarly, a species of flowering plant called Saussurea obvallata has been found at 6,150 meters.