What isn't obvious, but feels like it should be, is the rationale behind these Phenomenal Cosmic Powers of the baseband (with the attendant itty bitty living sp

What isn't obvious, but feels like it should be, is the rationale behind these Phenomenal Cosmic Powers of the baseband (with the attendant itty bitty living space). As an example, why does baseband need be able to modify OS RAM (assuming that it can do that). Is that a consequence of some sort of DMA for speed, or something else?