By boiling the Miranda rights down into an easily remembered warning, police can protect themselves against fraudulent abuse charges, as well as insure that each suspect has the same treatment before interrogation. As #2 says, there are tricks to get around any legal warning. Also, by specifically stating a suspect's right to remain silent, it is more damning when a suspect waives that right and confesses; confessions, especially when not recorded, are always automatically suspected of being coerced by the attorney.
Police officers are more aware of the rights of the arrested now. They are very careful to make sure they say the Miranda warning, and also stop questioning when the suspect asks for a lawyer. They still trick people though, and most everyone already knows the Miranda warning.