Welllll......
First, there are quite a few snake species that do feed on insectsSmooth Green Snakes, Rough Green snakes, Ground Snakes, Shovelnose snakes, Racers (Yes, they feed on locusts) etc.
For the small amounts of food comparative to the animal; it depends on the species. Brown Snakes (Storeria genus) feed on very small invertebrates. Some that are barely half the size of their heads. It all depends on what the species is designed for, and how they evolved.
As for the instincts on skipping the wrapping, and constriction...not entirely. I had quite a few giants, including a couple AfRocks, that would gently take F/T Rabbits straight from the tongs, and start to swallow. Nothing else to it. If the animal is dead, and they know so, then why waste the energy on a deceased meal? Don't forget, they do feed on carrion in the wild![]()