There's also the consideration from the ad network side of things. This gives Google a lot more power in the ecosystem than they had before in theory if lots of people switch to it (which they will, because they don't have much of a choice).

Similarly with Instant Articles--the big players own the ecosystem and can enforce whatever constraints they want if they have enough leverage. In this case, it happens to provide a sizable benefit to end users so publishers and ad networks are really the only ones feeling the pain.