Also there's the aspect of just... not caring. As someone who technically could read the email, browse the files, or track the apps installed and used on the phone of nearly any person where I work, any small bit of idle curiousity died before I was done my first day.
Even if I was nosy, 99% of people are just not that fucking interesting. What would even be the point of abusing my access?
I've seen someone put it like this: male gynecologists don't get excited looking at lady bits at work.