Better cooking skill should equal lower food poisoning chance?
Who says that the food poisoning is from poor cooking?
This is the zombie apocalypse. There are animals running around, many of which are already diseased and rotting. Who KNOWS how the zombie plague is affecting the deer, snakes, chickens, wolves, rabbits, and boars in the game. Are they diseased with some form of the zombie plague? are they just diseased in general? Sick?
There are also burned forests, rotting corpses, and radiation zones in the world...and we're drinking standing groundwater? We expect a little bit of boiling to completely remove the danger from doing that? We're also eating plants grown in compromised soil, affected by who knows what toxins and radiation. Heck, "rotting flesh" is even one of the ingredients in the farm plots. This flesh is diseased by some zombie-making super-plague, don't forget. And we're eating corn grown in it, and surprised when we get sick.
The lore, and common sense, completely supports the sickness chance from non-canned food.
What's more, it's a gameplay decision as well....If food should have a danger associated with it, and the Devs seem to think so, then they need to be somewhat balanced. canned food requires an up front risk of zombies and death and infection in order to loot it. It also isn't endlessly renewable. Grown food has no innate risk up front, but you COULD lose all the food you ate and more if the food poisoning hits. It requires an investment of time, effort, maybe skills, and land area though, so the risk for the grown food is tempered somewhat by the fact that if you CAN mass produce enough of it, then the risk of losing your food to food poisoning is significantly mitigated.