basically we're all trying to do the best for our snakes. some ways are tried, tested, publicised and generally adopted by the majority, other ways I've found work through personal experience and I'll adopt those methods. However the welfare of the snake should come first and foremost.
cornsnakes, ratsnakes, bullsnakes, boas and day geckos
i agree that in the wild snakes do not have heat mats to rely on for heat.
but...
in the wild they have more than 4x1.5 foot groung space to search for a hot place to thermoregulate and digest there food. so in conclusion i think a heat mat or other heat source is needed to help with digestion.