I don’t know what niche you inhabit, but anecdotally the overwhelming majority of engineers I know have consulted an RFC. RFCs are an active component in the Internet; you need to at least reference them (if not fully read them) to understand how various parts of the Internet interoperate.
(It seems extremely unlikely that the average non-junior engineer hasn’t opened up RFC 3339 or one of the HTTP caching RFCs, just for example.)
(It seems extremely unlikely that the average non-junior engineer hasn’t opened up RFC 3339 or one of the HTTP caching RFCs, just for example.)