Other body-only shapes have been getting smacked by bass, panfish and even catfish. The action must always be imparted rod tip twitches and slight reel handle turns causing the lure to wobble-dart & pause. A plausible reason is the greater time-in-place for a lure to aggravate fish to strike vs moving at a steady speed (i.e. crankbait or curl tail grub). I've found fish aren't usually in the mood to chase lures - at least not very far.
Vibration detection in fish is incredible and easily differentiates frequencies and various motions whether live or man-made. Lures in general don't mimic anything a fish eats but could get its digestive juices going due to unnatural shapes and actions lures possess. It's kind of like you or I checking out something we've never eaten but whose aroma gets and holds our attention. I would think the following sequence super important in a lure's success:
1. splash down
2. initial motion on the drop
3. motion and speed on the retrieve
Trout flies, feather and fur jigs are the most subtle lures going when it comes to shape, action and slow speed. Next in line are three shapes: the tailless body-lure shown above, and stinger (spike) tail) and the straight thin tail. All generate strikes from less than aggressive fish - the reasons speculative at best. Here are a few more:
