> Unless you're a proponent of panpsychism, we have to ask why living beings have it, but other natural processes do not.

No, we don't.

Because, while an individual may experience it, the conjecture that other things do or do not have it is without exception an unverifiable assumption, not an observed phenomenon which calls for an explanation.

> it's actually easier to conceive of a world like ours without subjective experience than one with it.

This is demonstrably false, because no experiencer can observe subjective experience other than their own, and, despite that, describing the world in terms of subjective experience occurring in a vast array of other beings beside the speaker is near-universal, to the point that we pathologize not viewing the universe that way.