Changing work can be costly, risky, difficult and just plain annoying. It may have negative consequences for the family and for your CV (imagine leaving your job soon after you realize what you _really_ are working on... and then again... and then being asked in an interview about that). These are all reasons enough to stop some people from simply changing a job once they realize it's not what they want to work on. Because oftentimes you don't know how you respond to something until you're in it.