it’s incredibly easy for them to install keyloggers and trackers remotely and silently.
And in here that’s very much illegal thing to do without prior consent from the employee and even with permission it’s requlated on what you can do with the data. Of course companies are permitted to restrict traffic and otherwise limit what users can do on the devices they’re given to, but it’s still illegal to spy individual users and what they do. Strong(ish) worker rights are a very nice thing to have around.