Legally, the computer is company property and thus company can do whatever they do with it (sometimes there are exceptions, like "stop looking if this looks like personal documents"). Even if there is no one manually looking at the specific computer, there is often antivirus/antimalware which reports to IT department. This makes sense -- if an employee went to a shady site on a work PC and got infected with malware, central IT should know ASAP about this to stop the spread / block stolen credentials. Even if the employee is unwilling to report it.

https://www.findlaw.com/employment/workplace-privacy/privacy...

The situation is different if the employee's personal computer is used -- then it can be expected to be full of personal stuff. This is why a lot of bigger places prohibit placing company code/credentials onto a personal device.