I understand, to some degree, the HTTP(S) response cache-control: headers, and associated controls for caching but the request cache-control: headers? How does a user control his own request headers? If users are using a normal browser, they have no ability to manually tweak any request parameters outside of those the URL itself indirectly generates.
How is request cache-control even a thing? Is it only intended for programmatically generated (curl, wget, JavaScript) HTTP(S) requests? or interaction between caches and origins?