It wouldn't surprise me if there's pressure from Dolby or the media companies to not do so, since Profile 7 is only used on BluRay (and the primary use case for playing back BluRays on Apple TVs I'm pretty sure is not playing backed-up personally-owned media). And, I'm sure Apple isn't losing many sales to not supporting it.

Lack of pass-through could probably be argued the same way, although it is a bit more surprising.