Here is my theory: because crappie beds are not as defined as gills, side imaging has a hard time picking up the nest indentation. Also, because side imaging is shooting up towards the shore, shadows of crappies on the bottom are hard to see.
Nice picture ShilohRed. For sideimaging to get a picture that defined is sometimes really hard, good job locating those beds. One day, maybe just one day I'll find some too.