For me it’s the paranoia surrounding webcams. People outright refuse to own one and I understand, until they go on and on about how they’re being spied. Here’s the secret - unplug the damn thing when you think you won’t use it or haven’t used it in a while.
They, whoever it is, can’t really spy on you on something that’s already off and unplugged!
While I’ve only used one or two types of bluetooth headphones, i’ve never hand any trouble replacing the battery with them. The cups just snap out and then you unplug the lithium cell and plug a new one it, at least in my experience, so that may just have been a thing with the model you got.