I think, as a general rule, people overestimate the value of their own skillsets/contributions and underestimate the skillsets/contributions of others. It is probably a Jedi mind trick to make ourselves feel more important/smarter/what have you. Luckily the free market for labor mostly exists (ignoring possibly shady deals between certain large tech companies) and people feeling undervalued can test that theory by shopping their skillset around. I think more people feel undervalued/underappreciated than pursue the "shopping around" angle. There are lots of reasons/excuses as to why, but protecting one's ego probably has a role, acknowledged or not.