How do you buy a strike when you pick it out of the dirt? If you get a strike on a ball in the dirt the batter swung or the ump is horrendous.
Catchers should block everything because it's the best way to get a good relationship with the ump. If you try to pick to many and they get hit they get ticked. Why make the guy who calls balls and strikes upset?
Plus it's good practice. Blocking drills in practice and bullpens are great but still not quite like doing it in a game.
Everyone is trying to get to the MLB level who plays baseball but we need to understand they can do things that 90% of all players at all levels cannot do.