They'll still be around, if we are, however long to come. I don't recommend them under most circumstances. Not that my approval is needed in most cases.

Plenty of reasons. Knowing whether I'm having a private conversation or one another person may be 'hearing' so to speak. Should things come to violence, I prefer to know what damage I am doing; yes they may be choosing to attack me and thus the feedback is a consequence for their actions. If that's the case, I am ethically in the clear. I still prefer to know. Understanding someone's poor mood may not be their own affects how you can help with it.

Those are some examples.