Why would I care that some device to which I never gave a shred of my personal information of any kind (e.g. not logging it into any online account) found an open public network that I don't use and that has no connection to me?

Sure, I would be disturbed that it's doing that sort of thing in spite of Wi-Fi being explicitly turned off.

What is the threat to me though?

Because it's acting with your IP address, so attempts to prevent whatever shady botnet things it gets up to may also interfere with legitimate use by humans on your network.

They have your location, and can detect your interests from what you watch, and fingerprint you. Things like this are pieces of a larger, comprehensive picture of your life.

Also, how do you pay for streaming channels, etc., if you don't give it any information?

Samsung TVs were literally recording people with microphones and doing voice recognition. Unless you don’t speak in your home, it will have you identified quite quickly.

It can record audio, sometimes video, and fingerprint what you watch on it. Proximity can be enough to identify you.

ACR

Because the TV is recording your voice, what you watch and possibly taking pictures, depending on the brand, and it needs a connection to send that information to whoever will pay for it.