Same thing as Dak throwing the football when he comes in.
I can remember one time he's kept it, and that was in the Troy game where we needed a big conversion late and he got like 15 yards out of it. But no need to do it unless we need to. At this point in the season the option part of the read option is clearly not in our plans to run much, so no need to give teams a look at Tyler keeping the ball on it.