I've always wondered the same thing. I've lived a reasonably stressful life, living through much worse things than the daily monotony of office life as a software engineer. However there are some days where it truly just crushes my spirits and leaves me completely spiritually depleted. There's truly something to be said regarding the elasticity of our mental health and how large a role expectations and norms play in our mental well-being. Not to mention there may be something particularly dehumanizing about the profession of software engineering.