Why food is spicy

[snopes]

Comment: [Not a new rumor, but......]

When it is mentioned in conversation that Mexican or Thai food tends to be
very spicy, people will often assert that this has a good reason, namely
to kill off bacteria in the (uncooked or undercooked) food (implying that
sanitary conditions in such countries are less than ideal, coupled with,
or due to, the prevailing hot weather).

Apart from failing to explain why the majority of tropical/sub-tropical
countries DON'T have a particularly spicy cuisine then, this theory has a
major flaw: Isn't hotness / pungency just a sensory impression of the
tongue/mucous membranes? How is this supposed to be harmful to a
bacterium? I cannot imagine that your average e.coli would be impressed by
this in the slightest, let alone die of the shock.