Removed from newer models due to part shortages / cost reduction. The software function removed from models with the hardware for consistency / to give the false impression that it wasn't a useful sensor and that the cars are not going backwards in capability.
Because those radars are low results and lead to false positive. The achieved better results with camera only.
Tesla bragged radar could bounce under the car ahead to react to the second car ahead stopping, even though the second ahead couldn't be seen. Removing radar was needed due to the electronic component shortage.
Musk mentioned this on twitter a number of years before, but it turned to not to be that practical with those radars.
That they were planning to remove radar was clear a while before but the electronic component shortage made it a higher priority problem.
So with camera only how do you determine if a paper bag on the highway is empty or full of metal objects?