ShotOne, although it probably isn't the same these days, in the AAR world we often used to say "The only thing you can be sure of is the time you planned to take-off" - because the entire mission could change from the moment you arrived for briefing. So a lot of thinking for yourself and working out how best to meet the mission needs - if weather wasn't suitable on the planned AAR area, you'd have to find another area and coordinate with the area controller. Even in UAS QFI-ing days, I'd think "Ah great - some aeros in the morning, then a couple of stalling trips this afternoon" or whatever.
So the fact that, as a senior 4-jet captain I was paid far less than an airline pilot wasn't an issue - my job was a lot more interesting than yet another 0-dark-00 trip to some holiday resort.
But that was before the RAF's variety of flying reduced, 'capability holidays' became common, contractors and FTRS started infiltrating the training world and front line flying meant more and more time away on detachment.
If Σ (W+£) = const., where W is enjoyment of work and £ is pay, in the RAF 'W' used to be much greater than it is today, I gather, whereas £ hasn't increased to compensate. So if £ is greater in the airlines, people will be more and more likely to accept a lower 'W' factor.
Or, in more crude terms,"When your bucket of fun is smaller than your bucket of $hit, it's time to leave!"