You are probably WRONG about many other things too.. d;-)~',',
The purpose was to make sure all the citizens understood their rights. Do you think it's a good thing if someone doesn't know their rights?
And if you think the SCOTUS made this decision so they could make the police look like drones and demoralize them you are incorrect. Not to mention disconnected from reality.
You can agree or disagree with the decision, but to characterize the motives of the judges in that way requires a vivid imagination.
Before this law, and even after, many LEOs lied to arrestees about their rights. That is a fact.
The truth is, it takes them off the hook by disallowing the defendants from claiming they didn't know their rights.
I have problems with the guilty not being held accountable because some imbecile didn't do his job. That part could be changed, but on balance, it was a good decision IMO.
Your mileage may differ.