Why did Venom only eat heads?

Venom needs food for himself other than food taken by Eddie for himself. Sometimes Venom prefers human flesh as food while Eddie has no interest in it.

In one scene when Eddie crashed with his motorcycle and Treece was about to capture him, Venom takes over and tries to eat Treece,saying

Eyes. Lungs. Pancreas. So many snacks, so little time.

So that makes me think, that Venom is ready to eat whole body of a human and he likes all of them.

My question is, why he only eat people's heads even when he likes every organ and also eating whole body is more food rather than just going for the head.

I know in the scene I mentioned above, he ate head of the one Drake's thug and he didn't have much time for eat whole human. but in later scenes Venom had enough time to eat whole human but he just bites off heads and eats'em.

Even in the final scene, we see Venom's desires on eating humans and he expresses he like to eat all. (and I think he did ate the whole bad guy at Mrs Chen's shop).

We will eat both your arms, and then both of your legs, and we will eat your face right off your head. You will be this armless, legless, faceless thing,rolling down the street,like a turd,in the wind.

Then why we mostly see Venom eat/bites off just only heads?