I think the main issue is that you don't expect a service to send anything related to your data without letting you know. Even if it's a ping "alive" sent to a server they own.

Imagine if your smart toilet would just send a small anonymized message to a urine sampling analysis service so it can let you you know your cholesterol levels are a bit high, totally anonymous, totally for your benefit. Maybe it's a great feature, but would anyone expect this to happen without consent / opt in?