SS - one other point:
Currently, the airline wannabe has to obtain the CPL and FI Rating before being permitted to instruct for remuneration. Many will be sorely out of pocket for years, so will obviously jump at the first chance of an airline job and the opportunity to reduce their debt accordingly.
Whereas a PPL holder can build up pre-FI time as and when without having to give up any other 'day job', then embark upon the course. As soon as they have passed, they can apply for an instructing position either full or part-time and save up for the 'fATPL' course. Which they will enter with rather more airmanship and experience than someone who has never flown before - and arrive at the airline with all that fATPL knowledge still fresh in their minds.