Yeah it's really frustrating. Hurts him and his rhythm, but it also hurts the team offense.
When he's on court, he's our most consistently efficient offensive player. He produces extremely high quality looks at an extremely high rate, and he passes well too which means he creates very good looks for others.
If he's on the floor and you don't show any interest in getting him involved in the offense at all, you're doing it wrong. That doesn't mean he has to be taking every shot, but as you say, 3 FGAs in an entire half is just unacceptable. There's no reason he should ever be taking fewer than 15 shots in a game unless something very weird is going on.