Odds of Hanging On
Between the high stress and the sleep deprivation, executive burnout is a real issue (source). Executives are expected to bring their A-game while working inside and outside of the office, and it's easy to see why the stresses of the job can eventually overwhelm some of them.
It's not that the higher-ups aren't committed to keeping their executives; billions of dollars are spent on bonuses and incentives to keep executives running like well-oiled machines. It's just that the work is nonstop and stressful; only the most resilient people can hang on for decade after decade of high-pressure, high-risk craziness.
For some executives, all those zeroes at the end of their bonus check are enough to keep them going. For others, the long hours and high competition is enough to make them throw their hands in the air and quit. You need to have a body and mind of steel in order to withstand all the stress this job will put you through.