DaGame,
I have an FCC license. The last time I checked, per FCC regulations you needed one to return aeronautical and shipboard radios to service. There is a radar endorsement too.
I got mine years ago when I was an aircraft mechanic. My leadman explained that eventually everything on an aircraft would have wires on it, if it didn't have already. That was in 1979.
Honestly, I never exercised it. That is to say, I might have gone to work as an Avionics Bench technician with it. I never did.
I worked as an aircraft electrician under my Airframe and Powerplant License at Eastern Airlines. Their internal policy for aircraft overhaul/heavy checks was to assign electro-mechanical work to the electrical group (people with A&Ps) while the folks in the Comm Nav group needed to have FCC licenses.
As an A&P in smaller outfits (repair stations, commuter airlines, flight line support) if it was broken you just fixed it. It didn’t matter if it was engine, hydraulic, gear, radar etc. Many folks made it easier to become a guru because they would shy away from electrical troubleshooting for whatever reason.
The last time I had a job providing engineering shop support for an avionics shop (I now have my BSEE), the people that repaired aircraft radars and radios were required to have their FCC. I don’t know who’s policy that actually was (FAA, FCC or Operators).
It all depends on your objectives I guess.