I don't necessarily like or willingly support it, But it is useful if applied right. From experience, Its an absolute must in high security operations. Email traffic must be retained for safety concerns, And leaks can be prevented by having emails filtered as they leave the facility like that. As far as site blocking etc. I personally have seen increases in productivity when people aren't glued to a PC reading reddit and are actually paying attention to their work. I have also seen these blocks be so burdensome that real work can only get done on a personal PC or at home. Ive even seen people in a meeting doing a powerpoint look something up on their phone versus the browser of the PC theyre on just because its faster to do. Rarely has IT actually provided the level of service that we need not to have to turn to outside inet sources … but part of that is the restrictions being thrust on them by gov't … so its a tightrope to walk really. The monitoring could be to a level where it actually causes more leaks than it saves because it incentivizes people to use hardware/software off their network. So it can be bad as well.
I work as an IT support and our company uses Worktime for monitoring login-out times. We actually get paid for overtimes as this software tracks login/logout time. It does not record my screen or take screenshots, So I feel okay. Also, They noticed noone was using one program, So they cancelled their subscription to it, So it was beneficial to the company as well
If an employer wants to monitor their own computer hardware and network this is completely fine. You as an employee have no right to privacy using their equipment to perform your duties - and if you decide to do personal things you may even be violating your terms of employment.
Also, Employers need to be compliant under law to be able to answer to an official investigation and must retain various records. Some of which may include what an employee is doing on the company owned computer.