The failure of hitters is very clearly and demonstrably proven to be the ever increasing nastiness of pitchers. They throw harder, use more frequent and more effective breaking balls, and the never-ending series of calls to the bullpen means there's always a new 100mph arm coming at you.

Swinging for the fences is not a matter of those damn kids these days that don't know what it means to hit for contact. It's a rational adaptation to the increasing difficulty in doing so. The harder it is to string together a series of singles, the more important it is to make those few hits count.