Because of Hand shake issues that are all over these forums.Why not? If you want the best sound you should use HDMI. What is the downside?
I used to use optical cable because I had no choice, it was an old receiver that didn't have HDMI inputs.
Lots of post in Directv and Dish forums saying something or another is a bug or not working, and then 5 posts later you realize they have their system running through HDMI through an audio receiver.
That should be your first trouble shooting test.
That's like posting a bug, that my Hopper won't power up, but you have it plugged into a switched outlet and didn't turn it on.
I'm fairly sure these companies don't care about your home audio systems.
I don't put components between my TV and devices.
Saves a lot of aggravation.
Samsung Galaxy S6 Active