I think we can interpret "browser extension" as a catch-all for "not directly built into the browser", in whatever form that takes.
Quite frankly I don't think it should be either. I'm sick of browsers trying to sidestep my operating system's networking stack (be it forcing their own DNS implementations for 'security' or now this BS).
There are other usecases that don't affect you which are very handy for others, such as testing site access from different countries with per-tab geo settings from a VPN extension.