A year or thereabouts before we secured the vastly superior military accreditation for civil pilot licences, as compared with the current dumbed-down nonsense thanks to 22Gp, people were studying in crewrooms or at home during non-flying times and leaving in large numbers. I recall one Dining-In Night at Brize at which 8 pilots were dined out for airline jobs....
Then came the 'proper' military accreditiation which had the desired retention result - and of course people still had sensible pension rights at ORD/NRD. We also had rather more varied flying to enjoy. We still had the option of QFI-ing at a UAS, for example - and the creeping cancer of contractorisation had yet to appear on the scene. In addition, there were rather more military aerodromes in the UK to which people could be posted.
Now there is virtually NO military accreditation, the RAF cannot seem to think outside the sandpit, pensions have been savaged, aerodromes have been closed and flying is become both rarer and more groundhog day in nature.
So it's hardly surprising that ATPL studies will dominate crewroom activity and that people will leave as soon as they can....