There are a few possibilities that would cause this. Crappie start to spawn when they're about 2-3 years old, and they often seem to target 10-14 inch crappie according to Minnesota DNR officials. Another possibility is that most crappie fish lie below the winter offshoots in deeper water anyway, so many stay there year round. It's also possible some fishermen have simply been fishing too shallow to find them without using live bait, which can increase the time and excitement of fishing for crappie.