Do as I say, not as I do.
To get into the seat of most aeroplanes doesn't come cheap, sure. To buy a rating in order to get into the right seat of a jet, well yes, now you can start thinking about harvesting organs.
It is indeed an alternative - but compared to paying your way into an airline? Thanks but no thanks. It's unappealing to many - slow, poorly paid and most of all - uncertain.