No one is indispensable. You understand this intellectually. If you are thoughtless and reckless, your behavior does not show you understand this fact. If you are timid and defensive, you have lost a huge opportunity to be the best you can be.
For some, the tug of “comfort” and “predictable” is stronger than the tug of “challenge” and “achievement.” Such people come to work and work hard only when they feel threatened in some way. It could be a reprimand, or the risk of losing their job, or some other “harm.” I even predict there is an attitude of entitlement lurking somewhere in their subconsciousness.
Organizations trying to stay nimble and agile look for ways to inject urgency and keep their employees off guard. This may be necessary as a management tactic from time to time. If not managed well, this could lead to stress and fatigue.
The real problem is that people evolve and change. Their needs change over their career life cycle. Thus the answer may be in “customized motivation.” In the perfect workplace, each employee gets a message that resonates with them at a visceral level. This is not easy to do, but the mere attempt will get positive benefits.