I know for a fact that you are correct about the RG100
But i think you are forgetting that most people use 1x12s or 2x12s these days, and only one of em
and to boot, the vast majority of people don't want to mess around with ohms ratings that aren't exact;y matched because they are terrified they are going to fry transformers
And there's also the sound issue (and i'm one of them) - I think guitar doesn't sound as pleasant at lower ohm ratings. Even 8 ohms (say with a boogie) just by default to me, doesn't sound as good as 16