To add to this:
https://www.espn.com/mlb/story/_/id/29430508/nl-managers-weigh-universal-dh
Last year's NL managers sound more pro-DH than anti-DH. Doing the same thing all the time, as Otto said, seems like an odd thing to cling to as "strategy". I mean, is asking your players to wear a glove in the outfield also strategy?
I ask that tongue-in-cheek, but when every NL manager pinch hits in the same situations, the same way, with the same switches and all that stuff....how different is it really?
Think of the worst hitter you can remember watching. Pedro Florimon. Some backup catcher. Whatever. Chances are, as bad as they were, they were still several factors better as hitters than your average pitcher. And that should make sense! Pitchers are trained and prepare to pitch. Asking them to hit too is just ridiculous and it yields exactly what you'd expect: utter futility. No other game forces a highly trained athlete to do something outside their skillset that is demonstrably subpar relative to their peers. NHL wings don't take turns playing goalie. NFL punters don't suddenly play nose tackle. NBA centers aren't suddenly required to heave only half court shots to score. All of those things sound silly because they are silly and the game would look silly to do it. It's no different every time I watch some dude flail at pitches in a jacket wishing he had the bunt sign on.