I hired a Chinese Haval Car for a weekend last year (Australia). It started beeping at me for being distracted because I was checking for traffic in the other lanes - which is crucial when driving in a 4 lane highway. Of cause, I had never experienced such a beep before, so I had to take my eyes off the road tp look at the screen to see what the reason for the beeping was. Then, on a multlane highway, I would indicat…
That is definitely not the point of a turning signal. The car that's already in the lane has right of way and it's your responsibility not to plow into them. If they opt to make room for you, great (that's just courteous driving), but it's not an obligation.
If you can't see the car in your blindspot when changing lanes, you're not doing a proper shoulder check, hence the blindspot warning.