Good question. I honestly think the pitchers like throwing to Smith more than they did to Contreras and Lucroy and we'll have to see about Vogt. I think they are trying to squeeze the last bit of offense out of Vogt until the return of d'Arnaud. Pitchers can be a finicky bunch about who they are throwing to (witness the rise of "personal catchers" throughout the majors) and that might be in play here.
