I'll answer that:
1) effective lack of control of your life
2) constant erosion of pay and benefits (below average pay raises/no pay raises)
3) extortionate staff travel costs (the newly hired pilots can't even afford to travel in J due cost)
4) if you are on the "wrong" fleet, you might as well be working for a different airline
5) unaccountable management
....you only wanted 5, could go on and on.