Most people aren't staying at their jobs because they're happy. They're staying because the alternative is worse. During the ZIRP era, you could spell javascript and earn yourself an offer elsewhere with a 20% salary increase. Now these days? You're competing against the largest pool of active, qualified candidates in your career. Interview processes are longer, more intense, and that's assuming you even hear back. Most people are sending hundreds of applications just to get a single call. To many folks currently employed, it's simply not worth it to see what else is out there.