In article , Mike Coslo writes:

More spectrum is simply the reward system in use. It was chosen in large
part because it's easy to enforce.


Another thought is that at HF frequencies, a inexperienced or poor
operator can propagate their signal over the whole world.

Under the right conditions, yes.

If I were to
be making a training ground for amateurs, it would be using line of
sight type signals

I disagree!

The greatest sustained period of growth in US amateur history was from the end
of WW2 until the mid-to-late 1980s. From 60,000 hams on VJ day to about 600,000
40 or so years later. And this included a period of almost no growth in the mid
1960s. Through most of that time, the training ground for new US amateurs was
predominantly HF.

73 de Jim, N2EY