In an ideal world, licences should not be necessary to operate radio transmitters - there, I've said it! Seriously, the RF spectrum is a natural resource and we should all be free to use it as we see fit. I don't need a licence to turn on a light in my house - which is transmitting electromagnetic radiation. I don't need a licence to shout to someone on the other side of the road - which is communicating remotely (albeit quite short range) - so why do I need a licence to operate an HF radio? If we look back a hundred years, then the answer is obvious - the section of the electromagnetic spectrum suitable for long distance communications is finite and quite narrow and there was a lot of competition for it. Titanic had sunk ten years earlier and that event demonstrated the high value of radio communications for safety-of-life applications. Entertainment broadcasting was beginning to take off and selling broadcasting licences was a big earner for governments. The military had got a taste of how liberating it is for a commander to be able to send instructions to his troops on the far side of the battlefield and know that the message will get there in milliseconds rather than having to wait for a vulnerable messenger to run the distance.
Now, things are changing rapidly. An HF radio will get your message round the world - sometimes! The MUF goes up and down like a yoyo and you have to chase it across the bands to find the right frequency to get through. The solar cycle means that there will be two or three years in every eleven when it becomes almost impossible to get through and a big geomagnetic storm can shut the entire HF spectrum down for a day or more. There were no satellites when Titanic sank - these days, the SOS would have gone out over Intelsat, not tapped out in CW on Top Band.
Broadcasters are retreating from RF - the internet is just so much cheaper to operate. The military and other government agencies are moving up to microwave frequencies - either point-to-point or relayed via satellite. Again, it's more predictable than HF propagation and the available data rate is far higher.
So, do governments still need to control access to HF through licencing? Probably yes, but it is a lot less important than it was and is getting still less important as time goes on. Gone are the days when an idiot with a Yaesu or ICOM on HF could cause interference that might endanger life. There's very little military or diplomatic traffic of any importance being transmitted on frequencies below 30MHz.
Martin (G8FXC)