Please enlighten us then, why do many countries require commercial kitchens have fire sprinklers if it's such a terrible and dangerous idea?

Most developed jurisdictions require commercial kitchens (and commercial spaces in general) to have fire suppression systems, not necessarily fire sprinklers. Water sprinklers are a common choice for fire suppression in many spaces because they're relatively cheap, but they're not the only option. A kitchen fire suppression system will generally be a wet chemical system that will safely blanket a grease fire while still being easy to clean off of food prep surfaces unlike dry chemicals.

Presumably because the regulations were written by people who have zero experience of either kitchens, fires, or kitchen fires.

Do you know what happens when you put water on an oil fire, which is pretty much what you're going to have in a kitchen?