Call it the opposite of defense-in-depth. Device manufacturers who aren't thorough might allow a class of "attacks" by way of using DNS. Having ubiquitous DoH takes away that "attack" vector.
I'm not arguing device manufacturers need DoH to be jerks. Having it available just enables the less sophisticated ones to be jerky more easily. DNS-over-TLS does the same thing, it's just marginally less frustrating because it can be blocked at the network layer, at least.
I understand that allowing owners of devices to do what they want on their own networks runs counter to the whole "protect the public from bad network operators" / "protect the public from bad people" narrative. I'm in the minority. It's just damned frustrating. It's sucking all the fun out of computing and networking. It's irrational and self-serving, but dammit it makes me angry.
You see, one thing is one or two vendors misusing protocols to remove users control from their devices. Another thing is an official protocol that does the same thing. We find have anywhere to run anymore.
As bi dollar corporations and organizations are more and more "protecting" ourselves they need to remove control from ourselves.