Any use of company resources for anything other than company business is not allowed in pretty much every company (although the vast majority don't care if you log into your bank or email account at lunch). However, there are limits on what the company can and can't do with employee information that is exposed to them that way. E.g. an employer can't use your login credentials obtained via use of work computers to access your private accounts.
The biggest threat - from my perspective - is not as much the evil corporation logging into my email account (while exposing itself to a massive lawsuit) but a weirdo Joe the IT guy who keeps switching jobs every two years, makes borderline comments about co-workers, and loves bragging about his crypto prowess.
People can do whatever they want but they assume the personal risk because there is virtually no privacy while on company resources.