Yes, it is only enabled while the car is parked.

That's a bit of a shortsighted comment, since it only works while the car is parked...

It's supposed to entertain while charging. Same with the games.

I would not be surprised if a lot of people elected to watch shows in their parked car instead of their living room simply because of the fantastic audio system.

I don't have a surround sound system in my home, but I do in my Model 3! Looking forward to trying it out :)

...to watch your favorite shows, movies and content right from your car while parked

I think it’s mostly for charging.

“YouTube, and Hulu or Hulu + Live TV accounts to watch your favorite shows, movies and content right from your car while parked.”