Scorekeeping on the defensive side of the ball is highly subjective. The St. Louis scorekeeper in particular is notoriously stingy with awarding assists. With this being said, I wouldn't expect Rams or Panthers IDPs to have many assists. Here is a great thread in the FBG IDP Forum that outlines assists awarded by stadium:
http://forums.footballguys.com/forum/index.php?showtopic=564151