Exactly. Why bother with BUIS on a rifle with a $2000 optic that is built like a tank and doesn't need batteries?
You're talking about back up sights, you only need them to be basic. They're not intended to be used other than in an emergency or when you're going through a building and want full field of view of your surroundings to hit someone who jumps out from behind a wall or some other close cover. They aren't made for target shooting at 100 yards.
The downsides to BUIS on a rifle that doesn't need them is increased cost, increased weight, more crap to snag on things, and they interfere with mounting your primary sight in it's optimal position.