Sometimes hot and vinegar is all you want.

There is a place for simple hot sauces, because you don't want to add additional flavours. Sometimes all you want is straight up chilis.

More complex hot sauces might include dried shrimp, fermented soy, lemon grass, dried mushrooms, but those flavours might not be desirable in some dishes. And some dishes require specific hot sauces because they are an integral part of the flavour profile (Mapo tofu, Tom Yum).