The only reason you see 4 WR sets is something bad happened before then. 3rd and really long or playing ketchup and needing to score a lot late in the game. The only time I WANT to see it is in 2minute offense at end of first half.4 receiver sets aren't so sickening if wr's #3 and #4 are pretty good and the qb can get rid of the ball quickly with accuracy. It can create mismatches against a teams worst secondary players. If wr's #3 and 4 are mediocre, then it can lead to picks or sacks. If Packer TE's take time to develop, the 4 wr set will make its appearance.