From what I can tell, they haven't had AV1 support in any chip yet. They said it didn't make the cut this time which probably means they just haven't finished and verified yet. Likewise, I'd guess Apples engineering efforts are more focused on upcoming, larger designs so they can finish moving off x86. Once those ship, they can refocus (plus it's another reason to upgrade your machine).
Rollout for most codecs is slow. I remember people saying no vp8/9 hardware decoders was deliberate too.
In truth, streaming companies want to save billions in data and licensing costs. Modern mobile SoCs can decode in software reasonably well, but with worse battery life. Netflix isn't paying for that, so they aren't incentivized to care past the most atrocious battery hogging behavior (it's not like you'll be streaming their exclusives from elsewhere). This leaves Qualcomm to implement it or get worse performance reviews.