Can you imagine how many police we'd need if there were an obligation to protect everyone at all times? There isn't a country on Earth with police forces that large.
And I doubt OP was speaking about those times when the country is entirely on fire or the police department has been nuked. Rather, I think the point is that the police will do anything they reasonably can do to help.
Note the last two words (in parentheses). That's the point being made: There aren't enough police to guarantee everyone protection.
Then we're talking past each other. That isn't what the Supreme Court decisions were about at all.