There are issues with this in the USA.
First a business does not want any unauthorized access from outside phones laptops. It's a recipe for disaster with virus's and potential access to sensitive information.
All communications from and to the company you want to monitor for reasons like what are people actually using the devices for and how do they deal with customers.
Big important part here is **** viewing and child ****. You can't have a hostile work place to other people. i.e. a male watching **** and upsetting female employees. Child **** or similar has to be watched for as it is a business allowing employees to do this. Imaging the negative publicity for the firm if they caught the person. Better to have company equipment standardized and monitored.