My wife's car is extremely aggressive. The second she turns it on, it steals my Bluetooth connection. I could be mowing my lawn, listening to music on my phone, then suddenly hear nothing, and it's because my wife got in her car and was suddenly blasted with my tunes.
I tell my phone to forget her car's Bluetooth connection, but then I'm constantly harassed by pop-ups on my phone every minute saying her car wants to pair with my phone. I can't get it to stop pinging me. It sees a Bluetooth device in range and then spams it, trying to connect.
So yes, I like to keep my Bluetooth off until I want to use it.