There are many reasons but the four most basic could be lack of
motivation and interest in the work, low pay, lack of growth and possibilities for development, and bad management. No matter how good a
job is people are going to be unsatisfied if they don't earn as much as
they need or if they have bosses that they don't think are good. One of
the main things that people also like is the prospect of going up the
rungs.
