Galactus eats planets primarily because he is hungry and requires vast amounts of energy to sustain himself.
Like any living being, Galactus consumes because he is hungry. However, his sustenance needs are on an cosmic scale. Given the enormous amount of Power Cosmic coursing through his being, he must satiate himself with vast quantities of energy. This immense energy requirement is the fundamental reason behind his devouring of entire planets and their life energies.
The Core Reason: Hunger
At the most basic level, Galactus consumes just like any other creature – driven by the need to feed. This fundamental hunger is the driving force behind his actions throughout the cosmos.
Sustaining the Power Cosmic
Galactus is an entity imbued with immense power known as the Power Cosmic. This incredible energy source requires a colossal amount of energy to maintain. The energy drawn from consuming worlds directly fuels and sustains his being, preventing him from succumbing to weakness or fading away.
Planets as the Necessary Sustenance
To meet the demand for "vast quantities of energy," Galactus requires a food source of unparalleled scale. Entire planets, rich in elemental and life energies, are the only known entities capable of providing the immense sustenance needed to satiate his cosmic hunger and maintain the Power Cosmic within him.
In essence, Galactus eats planets because his unique, energy-intensive existence necessitates a diet of cosmic proportions that only entire worlds can provide.
