The amounts of capsaicin I used to put in my food would function as a laxative for a vast majority of people. And had someone at that point stolen my food, I could've just eaten it and said "I like it spicy" and the thief would have zero recourse.

There is a small percentage of the population that would die if exposed to that much capacasin, however I assume that most of us do our best not to be exposed to pepper spray, or "tainted food." This does make it so we don't generally steal food, because there's a high probability that we will be allergic to the stuff.