I have the opposite experience: GrapheneOS has an option to automatically turn your bluetooth off after a configurable period of not being used. So when I need to use bluetooth, I turn it on like normal. Then, without thinking about it, it automatically turns off. The end result is my bluetooth is only ever on for a couple hours each month when I'm making phone calls.

With iOS the easiest way to make sure it off and stays off is to build a shortcut to cut off wifi/bluetooth. Otherwise it's typically off until you get geolocated as being back home/work and wifi comes back on.

I have a "store mode" button that just kills wifi/bt that I hit before I go into any store.

I miss wired headphones for this purpose. It's the only reason I even have BT enabled.

Android now has an option to enable it every day.. (I have it disabled).