The hierarchy can get super regimented in a lot of medicine -- university labs, especially hospitals, etc. Think med student / resident / intern / fellow / attendings / chief / etc., and nurses / nurse practitioners running on the side. My wife (md/phd fellow) currently works ~6 days a week, ~7a-7p, and with constant dangers of patients dying, being sued, and over-worked colleagues flipping out. Imagine everyone is on ops: everything is permanently on fire, you spend the morning learning about the latest fires, legal issues surrounding almost every action you take & hand-off, and getting waked up at night to deal with whatever went wrong with the day's plan.

Startups, and especially big tech, are relatively easy. More money etc., but no imminent risk of say death or infection.