Most companies don't want to spy on their employees' free time. They want to 1- make sure they are compliant with the law and their confidential stuff is secure and 2 - make sure that you are actually working for them when you say you are.
Installing something to listen to non-work related stuff serves neither of these goals, and would open them up to lawsuits and PR nightmares.
The people who decide the spyware must be installed are likely so far removed from the actual spyware and the people who admin it as to have no knowledge or understanding of the distinction.
Most companies don't want to spy on their employees' free time. They want to 1- make sure they are compliant with the law and their confidential stuff is secure and 2 - make sure that you are actually working for them when you say you are.
Installing something to listen to non-work related stuff serves neither of these goals, and would open them up to lawsuits and PR nightmares.