I see it as a perfect storm of pressures.
Working conditions:
-Steady decline in quantity/quality of compensation& benefits
-Hostile worker-HQ/exec relationship
-Longer hours, constant pressure to cut costs
Environment:
-Massive competitive pressure
-Aging planes, atrophying product: I would be dispirited to pass around Wal-Mart grade snack bags when in the past I offered decent roast dinners. Never mind the piano bars or the "MGM flights" with Paul Newman working the bar.*
Passengers:
1) Stressed from security
2) Feel squeezed by the fares (irrational with historic perspective; but flying a family of 4 at $400/pp return on the average American income would feel expensive)
3) Wonder where the full meal is. PanAm served one in F in 1982!
3a) Some genuinely awful arrangements (East Coast-Hawaii coach on UA)
4) Ill-behaved, tiresome, inexperienced, demanding, etc pax.
*One of my grandfather's favourite travel stories