Control
Most of the activity in a computer is started and controlled by programs, not directly by the user. These programs themselves are controlled by other programs, which again depend on others, and so on. There is interactivity between different levels of control, as well as between programs residing on the same level, so to speak.
In this sense “higher” programs are normally in no other way superior to those they control. Controlling is just a special function to be fulfilled, and often this is best done by programs as simple as possible. They neither have to know more than others, nor see everything happening elsewhere, usually they decide on the base of very few indices, following strict clear rules.
The same is true for programs that integrate others into one big one. Compared with the richness of those components, these central comprising parts are very often fairly simple, lacking every extra complexity that would harden the work of coordination. The more resources the core components consume for their own and for their task, the less is left for the rest, that means, above all: for the user.