Why does the number of fully metamorphosed insect species significantly exceed the number of incomplete metamorphosed insect species?

In insects with complete transformation, the larva does not compete with adults for territory and food (they may have different nutrition and a different habitat), for example: the larva of the May beetle develops in the soil and eats the roots of young plants, and the adult beetle lives in a ground-air environment , and feeds on leaves. And in insects that have incomplete transformation, the larva and the adult (imago) compete in everything (food, accommodation), the difference is that the larvae have underdeveloped wings and the reproductive system.