Here's why:

* Lipids are primarily composed of hydrocarbons: They consist of long chains of carbon atoms linked together with hydrogen atoms.

* The ratio of carbon to hydrogen is high: This makes hydrogen the most abundant atom by sheer volume.

* Oxygen is also present, but less abundant: Oxygen is found in the functional groups of lipids (like esters in triglycerides), but it's not as prevalent as hydrogen.

While carbon is the backbone of lipid structure, it's outnumbered by hydrogen atoms due to the hydrocarbon nature of these molecules.