I guess its what people are used to. If you start at HKA/HKE, then the grass is definitely greener at KA. Just down to pure terms and conditions. You might work a lot harder, but the housing, salary, other benefits far outweigh what is on offer at HKA/HKE.
No matter how bad things are at KA, I doubt anyone there would willingly join HKA/E. Anyone at KA disagree and I'm willing to eat humble pie.