> I don't need it, because I now keep my side mirrors set correctly I know where cars are beside me before the radar knows.
It's not there to replace you looking. It's there as an extra information source in case you make a mistake when looking. Maybe you're lucky with the your car, but even with curved ends of mirrors in mine, there's still a blind spot where I would not see a bike on the passenger's side and the little extra notification is great for that. It blinks for guard rails too, but that doesn't bother me - there's extremely rarely a reason to check the mirror on the side close to the rail.