"I wonder to what extent that the common reference to a degree as a backup for young people is rooted in parents in their 50s who remember a world where simply having a degree guaranteed a good job?"
Genghis,
Well, it's certainly been oversold in the USA...and continues to be.
As for US airlines requiring it from pilot applicants, it's necessary cuz they SAY it's required. Even with an airline listing a degree as "preferred", one has to ask how many of his competitors will still have one anyway. It's a jungle out there.