What's the point of body cameras if an officer has the option to turn it off or on. If they are going to use it, it should always stay on.
I don't think you want to hear/see me taking a bathroom break; what I'm talking to my wife about, etc.
I posted a link and a detailed list a little bit back on the responsibilities their officers have when it comes to body cams. Take a look.
When we wore them, we had to turn them on whenever we had any public interaction. We weren't required to have it on during private time unless something came up; i.e. eating lunch and someone walks up to us.
Always on is a bit ridiculous. Always on while performing your job is fine. They don't have infinite battery life. The ones we used 5+ years ago didn't last long at all. Our car cameras used VHS and we had to change the tapes out every six hours (they lasted 8) for our 12 hours shifts. Eventually, we backed it down to only having the car/body cams on when we had interactions with others. I always had my car cam on.