Generally IT / infrastructure / administrative are the most checked out, coasting, least engaged, least applied folks, with the exception being poorly designed environments where you're always dealing with outages. And of course there's high risk if you get it wrong.
Generally work that has a direct customer and user requirements, like application design (closer to the front end of an application) is more stressful, with API/backend layer less stressful. There's less pressure to deliver features and it's easier to apply straight SE principles without having to care as much about the end product. Generally the further you get away from end user customer deliverables, the less stress there is.
I have to highly, highly disagree given the context that in most SaaS software companies operations are going to be on-call, and horrific on-call nights can't happen if you're not on-call. Even in the best of companies (minus organizations that have the massive resources of a follow-the-sun on-call rotation) being on-call means tons of interruptions during one of the most important times you need to not be interrupted - sleeping.
What you may be observing is that the operations folks that make it to a later stage in their career that have not burned out permanently have adopted / maintained a mentality of simply not caring about work as much as possible.
Generally work that has a direct customer and user requirements, like application design (closer to the front end of an application) is more stressful, with API/backend layer less stressful. There's less pressure to deliver features and it's easier to apply straight SE principles without having to care as much about the end product. Generally the further you get away from end user customer deliverables, the less stress there is.