FLX/MCT hits the nail on the head. Why on earth should someone, when presented with the opportunity (and for a number of years it was a near certainty) to get a £40k a year job, say: "Actually, no.
Because the airline world is very cyclical and there's always a reasonable chance that there is no job, and you have to pay back £70k. With no job. And from reading posts, people have had no back up plans whatsoever.
There's a huge difference between servicing £25k and £70k debt and that's the issue. People seem to have signed up and not understood what a huge amount of money this is to earn after tax. It's terrifying.