Even though no electronics is involved, and it is a matter of simple
electrical
construction (some consideration given to constant impedance), how difficult
it is to manufacture our own plugs and sockets, despite that BNC and N have
been around for 70 years, with SMC some time later!

BTW, BNC is Bayonet Neill-Concelman, and not Bayonet Navy Connector
as some would believe. Neill created the N connector, and Concelman the C
connector and they combined forces to create the BNC (and TNC)