Egocentric reference frames can be far removed from body parts and the sensory surface, I think. Hemineglect shows an example. It’s neglect of the left or right side of the world, not always the exact same as the halves handled by the brain’s hemispheres. I imagine egocentric spaces are learned.
Egocentric spaces can help tie down the dimensions used in allocentric regions and abstract regions (I’m speculating here).
In allocentric regions, there are many object spaces but I think use the same dimensions in each region, e.g. 2d or 3d. That helps link objects into bigger one and reuse learned things (like how to move through allocentric space).
Different dimensions will be more useful for different objects, making it harder to pick just one set of dimensions during learning. Egocentric regions don’t have that problem, so they can help.
Likewise, egocentric regions can help tie down dimensions in abstract regions. If a set of dimensions is a way of thinking about a concept, it’s important to use a limited number. That helps link concepts together and reuse knowledge.
Things like language aren’t in abstract space themselves, but they can mirror abstract space with sensory/motor representation (e.g. hearing your own thoughts). Whereas concepts can be thought of in a bazillion ways, the equivalent representation in more tangible forms helps tie down the ways of thinking, because relatively consistent ways of thinking can be derived from those tangible representations.
Language is a way to represent abstract things in a unified way. It converts concepts to a sensory/motor representation. Hearing thoughts in your head feels like speaking and hearing. I imagine it’s easier to keep track of and grasp your own thoughts if you form a sensory representation.
There are other ways besides internal monologue (which some people don’t have whatsoever). Gut feelings seem like a way of representing abstract thought using subcortical emotions. It can be a literal gut feeling because people can feel different emotions mapped onto different parts of the body. Another way of thinking is in terms of actions.