Elements of a chilli sauce
Acid and Salt are preservatives. A bag of fresh chillies will rot within a month even in the fridge, a proper chilli sauce won't.

Also acid and salt are part of the common taste profile of most savoury dishes anyway, and if the sauce is used as an actual sauce e.g. on protein, these are welcome seasonings too.

Some famous types are rather close to the basic recipe: Sambal Oelek, Sriraja Panich etc.