Football trends come and go. Someone comes up with a new technique or drill, and everyone copies it until someone else comes up with a better solution. Down the road, a third person picks up a routine from the past, tweaks it a bit, and another wave of copiers copy the copier.
Generally, there is nothing nefarious about the copying process. It's just a bunch of people seeking a competitive edge, with targeting being one of those trends. Of course, I'm not referring to helmet-to-helmet hits but to using targets in drills to promote the accuracy of passers and snappers.
It seems to me there has been an uptick in the last decade of using targets to train quarterbacks and long snappers. It may be that the expansion of the short passing game and the need to put the ball into tight windows makes target practice more meaningful than when the focus was on the downfield game. Likewise, specialized long snappers and the high school snapper training and evaluation industry emphasize tools to make their students better.
The first use of targets on football practice fields appears to have been in 1913 when Derric Parmenter, Harvard's undersized but starting center in 1912, agreed to coach the Crimson centers while he remained on campus for medical school. Parmenter set up easel-like wooden sheets with aiming holes to drill his centers. In those days, of course, most offenses positioned the quarterback away from the center, and the center snapped the ball directly to a halfback or fullback -often as they were moving- so long snapping accurately to different locations was highly valued.