It is not beneficial to human organizations to have indispensable members. You can argue it's not good for the mental health of the indispensable people either.

When I first heard the quote in my first line, I thought it was cruel, inhumane and shockingly selfish on the part of employers. Nearly 30 years later, I see it almost entirely the other way around. Let's not build organizations full of indispensable people, but rather organizations in which tasks and expertise and stress and fear and success and joy are shared.