I imagine it is a combination of things. First is opportunity cost. If you give more time to someone like Hummel (and you’d have to if they are that far away on defense) that is less time for others who have a better chance to stick at catcher like McDonald or Feliciano. Also it seems like the more time is spent focusing on defense for catching the more the offense stalls (see Nottingham’s down year or two or Harrison this year). If you think the chance of the defense coming around is slim, do you want to stall the offensive progress as well? Well, maybe if you have a good bat (a Cooper Hummel, a David Fry, or the since-traded KJ Harrison) maybe you don't sweat the defense so much. Henry Blanco was a black hole at catcher when he was with the Brewers, and they had a better option in Raul Casanova. Dave Nilsson was a good option behind the plate, but they went with Mike Matheny - and gave up about 150 points of OPS for at least three years. I've seen Jason Kendall, Johnny Estrada, Damian Miller, and Chad Moeller, among others, just be offensive black holes. I liked having an offensive threat like Lucroy there. I want Lucroy back, or the next Lucroy. If there is one position on the field where you can't really cheat defensively, it's catcher. Lucroy was also a terrific defensive catcher, which is part of what made him so valuable. Casanova and Nillson were crap defenders, hence why they were replaced. You can play around with bad defense in the corner infield and outfield, but you don't really want to mess with that up the middle of the field.